source
stringclasses 1
value | task_type
stringclasses 1
value | in_source_id
stringlengths 1
8
| prompt
stringlengths 209
40.4k
| gold_standard_solution
stringlengths 0
56.7k
| verification_info
stringclasses 1
value | metadata
stringlengths 138
225
| problem_id
stringlengths 9
10
|
|---|---|---|---|---|---|---|---|
stackexchange | llm_judgeable_groundtruth_similarity | 17649 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I think singleton sets $\{x\}$ where $x$ is a member of $\mathbb{R}$ are both open and closed. Singleton sets are open because $\{x\}$ is a subset of itself. There are no points in the neighborhood of $x$. I want to know singleton sets are closed or not.
Now provide the response and nothing else.
| As has been noted, the notion of "open" and "closed" is not absolute, but depends on a topology . So in order to answer your question one must first ask what topology you are considering. A topological space is a pair, $(X,\tau)$, where $X$ is a nonempty set, and $\tau$ is a collection of subsets of $X$ such that: $\emptyset$ and $X$ are both elements of $\tau$; If $A$ and $B$ are elements of $\tau$, then $A\cap B$ is an element of $\tau$; If $\{A_i\}_{i\in I}$ is an arbitrary family of elements of $\tau$, then $\bigcup_{i\in I}A_i$ is an element of $\tau$. The elements of $\tau$ are said to be "open" (in $X$, in the topology $\tau$), and a set $C\subseteq X$ is said to be "closed" if and only if $X-C\in\tau$ (that is, if the complement is open). In $\mathbb{R}$, we can let $\tau$ be the collection of all subsets that are unions of open intervals; equivalently, a set $\mathcal{O}\subseteq\mathbb{R}$ is open if and only if for every $x\in\mathcal{O}$ there exists $\epsilon\gt 0$ such that $(x-\epsilon,x+\epsilon)\subseteq\mathcal{O}$. You may want to convince yourself that the collection of all such sets satisfies the three conditions above, and hence makes $\mathbb{R}$ a topological space. This topology is what is called the "usual" (or "metric") topology on $\mathbb{R}$. If you are working inside of $\mathbb{R}$ with this topology, then singletons $\{x\}$ are certainly closed, because their complements are open: given any $a\in \mathbb{R}-\{x\}$, let $\epsilon=|a-x|$. Then $x\notin (a-\epsilon,a+\epsilon)$, so $(a-\epsilon,a+\epsilon)\subseteq \mathbb{R}-\{x\}$; hence $\mathbb{R}-\{x\}$ is open, so $\{x\}$ is closed. The reason you give for $\{x\}$ to be open does not really make sense. Every set is a subset of itself, so if that argument were valid, every set would always be "open"; but we know this is not the case in every topological space (certainly not in $\mathbb{R}$ with the "usual topology"). So that argument certainly does not work. So: is $\{x\}$ open in $\mathbb{R}$ in the usual topology? Well, $x\in\{x\}$. Does there exist an $\epsilon\gt 0$ such that $(x-\epsilon,x+\epsilon)\subseteq \{x\}$? If so, then congratulations, you have shown the set is open. If there is no such $\epsilon$, and you prove that, then congratulations, you have shown that $\{x\}$ is not open. | {} | {'log_upvote_score': 7, 'links': ['https://math.stackexchange.com/questions/17649', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/5049/']} | jdg_70641 |
stackexchange | llm_judgeable_groundtruth_similarity | 12404 |
Below is a question asked on the forum reverseengineering.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
A typical PIN code snippet looks like this (taken from the official manual ): // This function is called before every instruction is executed// and prints the IPVOID printip(VOID *ip) { fprintf(trace, "%p\n", ip); }// Pin calls this function every time a new instruction is encounteredVOID Instruction(INS ins, VOID *v){ // Insert a call to printip before every instruction, and pass it the IP INS_InsertCall(ins, IPOINT_BEFORE, (AFUNPTR)printip, IARG_INST_PTR, IARG_END);} I just can't figure out how to access the ins object from within printip(VOID *p) . The other way round seems easy, i.e. getting the IP from from the ins object: INS_Address (INS ins) (see here ) I tried passing a INS *ins pointer to printip(VOID *ip, INS *ins) ins via IARG_PTR, &ins but this ended in either casting errors or Segmentation faults. How can I access the ins object (type INS ) from inside an analysis function? Side note: I got to this problem when trying to call INS_Disassemble (INS ins) for every executed instruction.
Now provide the response and nothing else.
| You may note that printip is a function pointer, it is lazily called internally by Pin ; moreover ins is an automatic variable (it is passed into Instruction from the stack). Consequently, passing &ins into printip (through IARG_PTR ), then using it will lead to segmentation faults. Pin declares INS by specializing the class template INDEX , as you can observe the following declaration in type_core.TLH : /*! @ingroup INS_BASIC_APIHandle for INS */ typedef class INDEX<6> INS; where constructors and assignment operators of class template INDEX are both default. So, in principle ^^, we can always declare a persistent variable to share an object of INS between instrumentation and analysis functions, for example: static INS per_ins;...VOID Instruction(INS ins, VOID *v){ per_ins = ins; ...}...VOID printip(VOID *ip){ INS_Disassemble(per_ins);} This method does not work, unfortunately, this is an example for "well-typed program still can go wrong" in C/C++ ^^. Since Pin does not guarantee that internal variables, accessed by an object of type INS , are persistent in analysis time , the result of calling INS_Disassemble(per_ins) in an analysis function can be meaningless. For your case, you may not want to call INS_Disassemble(ins) each time ins executes. We don't need that, for example, if ins is in a loop then this function will be called multiple times (with the same ins ) to get the same result. All static information of an instruction (e.g. the disassembled form of ins in this case) should be obtained in instrumentation time . Particularly, INS_Disassemble should be called single time only in some instrumentation function. One way to obtain the same effect as you want is: static std::unordered_map<ADDRINT, std::string> str_of_ins_at;VOID Instruction(INS ins, VOID *v){ str_of_ins_at[INS_Address(ins)] = INS_Disassemble(ins); ...}VOID printip(VOID *ip, ADDRINT addr) { std::string ins_str = str_of_ins_at[addr]; ...} | {} | {'log_upvote_score': 4, 'links': ['https://reverseengineering.stackexchange.com/questions/12404', 'https://reverseengineering.stackexchange.com', 'https://reverseengineering.stackexchange.com/users/11830/']} | jdg_70642 |
stackexchange | llm_judgeable_groundtruth_similarity | 59684195 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm working on a project where I need to replace the old ExpFoo with a new ExpFoo. An example would be an ExpFoo ((x * y) + (x * z)) is given and we have new IntFoo, 2, which will replace the Varfoo, x. And we have a PlusFoo (a + b), which will replace the Varfoo, y. So the result will be: ((2 * (a + b) + (2 * z)) Here's how it looks on the Main class: import java.util.Arrays;public class Main {public static void main(String[] args) { ExpFoo e1 = new IntFoo(1); ExpFoo e2 = new IntFoo(2); ExpFoo e5 = new IntFoo(5); ExpFoo x = new VarFoo("x"); ExpFoo plus = new PlusFoo(e1, e2); ExpFoo times = new TimesFoo(e5, x); ExpFoo bigTimes = new TimesFoo(plus, times); ExpFoo[] exps = { e1, e2, e5, x, plus, times, bigTimes }; System.out.println(Arrays.toString(exps)); Replacement r = new Replacement(); r.put(new VarFoo("x"), new PlusFoo(e1, e5)); System.out.println(r); for (ExpFoo exp : exps) { System.out.println(exp + " has " + exp.numberOfNodes() + " nodes and after applying " + r + " the value " + exp.computeValue(r)); } ExpFoo ex1 = new PlusFoo(new TimesFoo(new VarFoo("x"), new VarFoo("y")),new TimesFoo(new VarFoo("x"), new VarFoo("z"))); Replacement repl = new Replacement(); repl.put(new VarFoo("x"), new IntFoo(2)); repl.put(new VarFoo("y"), new PlusFoo(new VarFoo("a"), new VarFoo("b"))); ExpFoo ex2 = ex1.applyReplacement(repl); System.out.println("ex1: " + ex1); System.out.println("ex2: " + ex2);}} I have two issues: I cannot get the values of times and bigTimes. I cannot get applyReplacement(repl) to work. For the first issue, I couldn't get the values of ExpFoo times = new TimesFoo(e5, x); and ExpFoo bigTimes = new TimesFoo(plus, times); to use exp.computeValue(r) because I couldn't work out on how to calculate 1 + 5 to 6. All I've got was an exception that says: UnsupportedOperationException: Cannot compute the value of a varfoo without a replacement! For times, it should return as (5 * x) has 3 nodes and after applying [x:=(1 + 5)] the value 30 For bigTimes, it should return as ((1 + 2) * (5 * x)) has 7 nodes and after applying [x:=(1 + 5)] the value 90 For the second issue, I'm having a problem with ExpFoo ex2 = ex1.applyReplacement(repl); It returns an exception TimesExpFoo cannot be cast to class com.company.VarFoo I couldn't get it to work. It should return as ((2 * (a + b) + (2 * z)) I'm not allowed to create instance variables to all the classes except Replacement. I cannot use generics in all classes either. Here's the illustration on how it works, the Replacement class is separated in all classes. UML image here For the classes, this is what I've done so far. Varfoo class: import java.util.Set;/*** A VarFoo is a symbolic ExpFoo that stands for a value that has not yet* been fixed. A VarFoo has a name of the format* letter (letter | digit)^** (where '(letter | digit)^*' stands for 'a string of length 0 or more that* contains only letters and digits').* Here the class methods Character.isLetter(char) and* Character.isLetterOrDigit(char) determine whether a character is* a letter/a letter or a digit, respectively.* Instances of this class are immutable.*/public class VarFoo implements ExpFoo {/** * Name of this VarFoo. Non-null, of the format * <p> * letter (letter | digit)* */private String name;/** * Constructs a new VarFoo with the specified name. * * @param name must not be null; must be a String of the format letter * (letter | digit)^* */public VarFoo(String name) { this.name = name;}@Overridepublic int numberOfNodes() { return 1;}@Overridepublic int computeValue() { throw new UnsupportedOperationException("Cannot compute the value of a varfoo without a replacement!");}@Overridepublic int computeValue(Replacement repl) { //TODO;}@Overridepublic ExpFoo applyReplacement(Replacement s) { //TODO}@Overridepublic boolean isVarFooFree() { // TODO return true;}@Overridepublic Set<VarFoo> getVarfoo() { return null;}@Overridepublic void collectVarfoo(Set<VarFoo> vars) { for (char c : name.toCharArray()) { if (Character.isAlphabetic(c)){ vars.add(new VarFoo(name)); } }}@Overridepublic String toString() { return name;}/** * The method returns true if o is an instance of class VarFoo * whose name is equal to the name of this VarFoo; otherwise it * returns false. * * @return whether this VarFoo and Object o are equal */@Overridepublic boolean equals(Object o) { if (o == null) return false; if (!(o instanceof VarFoo)) return false; if (o == this) return true; return name.equals(((VarFoo) o).name);}@Overridepublic int hashCode() { int prime = 31; int result = 1; result = prime * result + ((name == null) ? 0 : name.hashCode()); return result;}} Replacement class: import java.util.HashMap;import java.util.Map;/*** A Replacement represents a mapping of finitely many VarFoo to* ExpFoo. One can construct an empty Replacement, update a Replacement* by adding/replacing/forgetting mappings of VarFoo to ExpFoo, and* query Replacements for the value to which they map a varfoo, whether they* have a mapping for a specific varfoo, and for a String representation.*/public class Replacement {private Map<VarFoo, ExpFoo> replacementMap;/** * Constructs an empty Replacement (i.e., a Replacement that does not * hold mappings for any varfoo(s). */public Replacement() { replacementMap = new HashMap<>();}/* Mutators *//** * Associates the specified ExpFoo with the specified Varfoo in this * Replacement. If the Replacement previously contained a mapping for the * Varfoo, the old ExpFoo is replaced. * * @param var the Varfoo with which exp is to be associated * @param exp the ExpFoo to which var is to be mapped * @return the ExpFoo to which var was mapped so far, or null if var did * not yet have a mapping in this Replacement * @throws NullPointerException if var or exp is null */public ExpFoo put(VarFoo var, ExpFoo exp) { return replacementMap.put(var, exp);}/** * Forgets the mapping for the specified Varfoo. Does not modify this * Replacement if it does not have a mapping for the specified Varfoo. * * @param var the Varfoo for which we want to forget the mapping * @return whether a mapping for var was forgotten due to the method call * @throws NullPointerException may be thrown if var is null */public boolean forget(VarFoo var) { if (var == null) { return true; } else { replacementMap.clear(); return true; }}/* Accessors *//** * Returns the value to which the specified Varfoo is mapped, or null if * this Replacement contains no mapping for the specified Varfoo. * * @param var the Varfoo for which we want the corresponding ExpFoo to * which it is mapped * @return the ExpFoo to which this Replacement maps var, or var if * this Replacement does not have a mapping for var * @throws NullPointerException may be thrown if var is null */public ExpFoo get(VarFoo var) { return replacementMap.get(var);}/** * Returns whether this Replacement has an explicit mapping of var to an * ExpFoo. * * @param var the Varfoo for which we want to know if this Replacement * has a mapping * @return whether this Replacement has an explicit mapping of var to an * ExpFoo * @throws NullPointerException may be thrown if the parameter is null */public boolean hasMappingFor(VarFoo var) { return replacementMap.containsValue(var);}@Overridepublic String toString() { String s = ""; for (Map.Entry<VarFoo, ExpFoo> ReplacementKey : replacementMap.entrySet()) { s = "[" + ReplacementKey.getKey() + ":=" + ReplacementKey.getValue() + "]"; } return s;}} ExpFoo class: import java.util.LinkedHashSet;import java.util.Set;/*** Basic interface for arithmetic ExpFoo. Implementations are expected to* be immutable, i.e., after object creation, the object's state cannot change,* and there are no mutator methods in any class that implements this interface.*/public interface ExpFoo {/** * Computes the number of sub-ExpFoo of this ExpFoo (its "size"). * * @return the number of nodes of this ExpFoo. */int numberOfNodes();/** * Computes the int value represented by this ExpFoo object. This * ExpFoo object must not contain Varfoos. * * @return the int value represented by this ExpFoo */int computeValue();/** * Computes the int value represented by this ExpFoo. * * @param repl * to be used to assign values to this ExpFoo; must not be * null * @return the int value represented by this ExpFoo * @throws UnsupportedOperationException * if the ExpFoo with repl applied to it still has * Varfoo * @throws NullPointerException * if s is null */default int computeValue(Replacement repl) { ExpFoo specialised = applyReplacement(repl); return specialised.computeValue();}/** * Returns whether this ExpFoo is VarFoo-free, i.e., none of its * direct or indirect sub-ExpFoo is a VarFoo object. * * @return whether this ExpFoo is VarFoo-free, i.e., none of its * direct or indirect sub-ExpFoo is a VarFoo object. */boolean isVarFooFree();/** * Returns the Set of Varfoo of this ExpFoo. The returned Set may be * modified. * * @return the Set of Varfoo of this ExpFoo */default Set<VarFoo> getVarfoo() { Set<VarFoo> result = new LinkedHashSet<>(); collectVarfoo(result); return result;}/** * Adds all Varfoo in this ExpFoo to vars * * @param vars * Varfoo will be added here; parameter must not be null * @throws NullPointerException * if vars is null */void collectVarfoo(Set<VarFoo> vars);/** * Applies a Replacement to this ExpFoo and returns the result. * * @param r * a Replacement to be applied to this ExpFoo; must not be * null * @return a version of this ExpFoo where all Varfoo have been * replaced by the values stored in s for the Varfoo * @throws NullPointerException * if s is null */ExpFoo applyReplacement(Replacement r);} BinaryFoo class: import java.util.Set;/*** Abstract class for ExpFoos with two direct subExpFoos. Provides an* implementation for numberOfNodes() method. Instances of this class are immutable.*/public abstract class BinaryFoo implements ExpFoo {/** the left subExpFoo; non-null */private ExpFoo left;/** the right subExpFoo; non-null */private ExpFoo right;/** String representation of the operator symbol; non-null */private String operatorSymbol;/** * Constructs a BinaryFoo with left and right as direct * subExpFoo and with operatorSymbol as the String representation of * the operator. * * @param left * the left subExpFoo; non-null * @param right * the right subExpFoo; non-null * @param operatorSymbol * String representation of the operator symbol; non-null */public BinaryFoo(ExpFoo left, ExpFoo right, String operatorSymbol) { if (left == null) { throw new NullPointerException("Illegal null value for left!"); } if (right == null) { throw new NullPointerException("Illegal null value for right!"); } if (operatorSymbol == null) { throw new NullPointerException( "Illegal null value for operatorSymbol!"); } this.left = left; this.right = right; this.operatorSymbol = operatorSymbol;}/** * Getter for the left subExpFoo. * * @return the left subExpFoo */public ExpFoo getLeft() { return left;}/** * Getter for the right subExpFoo. * * @return the right subExpFoo */public ExpFoo getRight() { return right;}/** * Getter for the operator symbol. * * @return the operator symbol */public String getOperatorSymbol() { return operatorSymbol;}@Overridepublic int numberOfNodes() { return 1 + left.numberOfNodes() + right.numberOfNodes();}@Overridepublic void collectVariables(Set<VarFoo> vars) { vars.add((VarFoo)left); vars.add((VarFoo)right);}@Overridepublic boolean isVarFooFree() { // TODO return false;}@Overridepublic String toString() { return "(" + left + " " + operatorSymbol + " " + right + ")";}@Overridepublic boolean equals(Object o) { if (!(o instanceof BinaryFoo)) { return false; } BinaryFoo other = (BinaryFoo) o; // relies on instance variables being non-null return operatorSymbol.equals(other.operatorSymbol) && left.equals(other.left) && right.equals(other.right);}@Overridepublic int hashCode() { int result = (left == null) ? 0 : left.hashCode(); result += (right == null) ? 0 : right.hashCode(); return result;}} TimesFoo class: /*** Represents an ExpFoo of the form e1 * e2.* Instances of this class are immutable.*/public class TimesFoo extends BinaryFoo {/** * Constructs a TimesFoo with left and right as direct * subExpFoo. */public TimesFoo(ExpFoo left, ExpFoo right) { super(left, right, "*");}@Overridepublic int computeValue() { return getLeft().computeValue() * getRight().computeValue();}@Overridepublic int computeValue(Replacement subst) { return computeValue();}@Overridepublic ExpFoo applyReplacement(Replacement r) { ExpFoo e = s.get((VarFoo)getVarFoo()); return e;}@Overridepublic boolean equals(Object o) { if (!(o instanceof TimesFoo)) { return false; } return super.equals(o);}@Overridepublic int hashCode() { return super.hashCode();}} PlusFoo class: /*** Represents an ExpFoo of the form e1 + e2.* Instances of this class are immutable.*/public class PlusFoo extends BinaryFoo {/** * Constructs a PlusFoo with left and right as direct subExpFoos. * * @param left the left subExpFoo; non-null * @param right the right subExpFoo; non-null */public PlusFoo(ExpFoo left, ExpFoo right) { super(left, right, "+");}@Overridepublic int computeValue() { return getLeft().computeValue() + getRight().computeValue();}@Overridepublic ExpFoo applyReplacement(Replacement r) { ExpFoo e = s.get((VarFoo)getVarFoo()); return e;}@Overridepublic int computeValue(Replacement repl) { return computeValue();}@Overridepublic boolean equals(Object o) { if (!(o instanceof PlusFoo)) { return false; } return super.equals(o);}@Overridepublic int hashCode() { return super.hashCode();}} IntFoo class: import java.util.Objects;import java.util.Set;/*** ExpFoo that represents an int value.*/public class IntFoo implements ExpFoo {/** * Stores the encapsulated value. */private int value;/** * Constructs a new IntFoo encapsulating value. * * @param value to be encapsulated in this IntFoo */public IntFoo(int value) { this.value = value;}/** * @return the int value this IntFoo stands for */public int getValue() { return value;}@Overridepublic int numberOfNodes() { return 1;}@Overridepublic int computeValue(Replacement repl) { return computeValue();}@Overridepublic int computeValue() { return value;}@Overridepublic ExpFoo applyReplacement(Replacement r) { VarFoo var = new Variable(name); //error ExpFoo e = s.get(var); return e;}@Overridepublic boolean isVarFooFree() { // TODO return false;}@Overridepublic Set<VarFoo> getVarfoo() { return null;}@Overridepublic void collectVarfoo(Set<VarFoo> vars) {}@Overridepublic String toString() { return "" + value;}@Overridepublic boolean equals(Object o) { if (o == null) return false; if (!(o instanceof IntFoo)) return false; if (o == this) return true; return value == (((IntFoo) o).value);}@Overridepublic int hashCode() { return Objects.hash(value);}}
Now provide the response and nothing else.
| I have solved this issue using the latest API available for this thing from AWS SDK for NodeJS using the following code: const aws = require('aws-sdk');const AWS_SIGNATURE_VERSION = 'v4';const s3 = new aws.S3({ accessKeyId: <aws-access-key>, secretAccessKey: <aws-secret-access-key>, region: <aws-region>, signatureVersion: AWS_SIGNATURE_VERSION});/** * Return a signed document URL given a Document instance * @param {object} document Document * @return {string} Pre-signed URL to document in S3 bucket */const getS3SignedDocumentURL = (docName) => { const url = s3.getSignedUrl('getObject', { Bucket: <aws-s3-bucket-name>, Key: <aws-s3-object-key>, Expires: <url-expiry-time-in-seconds>, ResponseContentDisposition: `attachment; filename="${docName}"` }); return url;};/** * Return a signed document URL previewable given a Document instance * @param {object} document Document * @return {string} Pre-signed URL to previewable document in S3 bucket */const getS3SignedDocumentURLPreviewable = (docName) => { const url = s3.getSignedUrl('getObject', { Bucket: <aws-s3-bucket-name>, Key: <aws-s3-object-key>, Expires: <url-expiry-time-in-seconds>, ResponseContentDisposition: `inline; filename="${docName}"` }); return url;};module.exports = { getS3SignedDocumentURL, getS3SignedDocumentURLPreviewable}; Note: Don't forget to replace the placeholders (<...>) with actual values to make it work. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/59684195', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/12689865/']} | jdg_70643 |
stackexchange | llm_judgeable_groundtruth_similarity | 7553607 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
We have a website application that is deployed and customised for multiple customers, across different domains, we are developing a Facebook Connect app within this website, so people can see what their friends are doing through our sites. I've set the site url and canvas url in my Facebook app to my localhost for debugging, I was wondering, what if I wanted to use this application across multiple domains? Will facebook only allow postback to one domain per application? Is it possible to configure multiple domains? EDIT If this isn't possible how are large companies managing multiple domains? Will it have to be setup as one domain per application or is there a way to programatically add a new application through code? EDIT There is further discussion on this issue here
Now provide the response and nothing else.
| Unfortunately, the September 30, 2011 blog post is worded in a misleading way. The relevant section is "Support for Multiple Domains in the Developer App." Reading that paragraph, it would appear that there are no restrictions in terms of which domains can be lumped together under one application. However, when I tried adding a second domain to an existing application, I received an error message saying that the new domain must be derived from the Site URL. One comment on that blog post described a similar experience. And that restriction was confirmed by a reply to that comment by someone in Developer Relations at Facebook, explaining that "All app domains must be derived from the site URL." I believe the confusion arises from incorrect wording in the post itself, which says "Your App’s URL (Website and/or Mobile Web URL) must be derived from one of the domains listed in the App Domain field." *Update: Just to clarify what types of domains are allowed, let's say your Site URL is "mywebsite.com". You would be allowed to add "mywebsite.co.uk" as an additional App Domain, but you would not be allowed to add "myalternatewebsite.com". | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/7553607', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/628372/']} | jdg_70644 |
stackexchange | llm_judgeable_groundtruth_similarity | 231204 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Let $\lbrace u_n \rbrace$ be a sequence defined by : $u_1=1$, $u_{n+1}=u_{n}+\dfrac{u_{n}^{2}}{a}$ for a be a positive real constant.Find : $\text{lim}_{n\rightarrow \infty}\left(\dfrac{u_1}{u_2}+...+\dfrac{u_n}{u_{n+1}}\right)$ If I denote $S_n$ by $\dfrac{u_1}{u_2}+...+\dfrac{u_n}{u_{n+1}}$ then $S_n$ is increasing sequence, but I could not prove that it is bounded above. May be $\text{lim}_{n\rightarrow \infty} S_n =\infty$ ? Please help me to solve it. Thanks
Now provide the response and nothing else.
| Shortly after finishing the proof, I realized that it is sufficient to observe the following identity $$ \sum_{k=1}^{n} \frac{u_k}{u_{k+1}} + \frac{a}{u_{n+1}} = a $$ and the fact that $u_{n} \to \infty$ as $n\to\infty$. Indeed, $$ \frac{a}{u_n} = \frac{u_n + a}{u_n + \frac{u_n^2}{a}} = \frac{u_n + a}{u_{n+1}} = \frac{u_n}{u_{n+1}} + \frac{a}{u_{n+1}}$$ and since $u_1 = 1$, the identity follows. Then by noting that $$ u_{n} \geq u_{n-1}^2 \geq \cdots \geq (u_2)^{2^{n-2}} \to \infty \quad \text{as} \quad n\to\infty, $$ the conclusion follows. I leave my old and sophisticated proof, which served a motivation. Finally I succeeded in proving my observation that $$ \sum_{n=1}^{\infty} \frac{u_n}{u_{n+1}} = a.$$ Step 0. Notation By the substitution $u_n = \dfrac{a}{x_n}$, we have$$ x_1 = a, \qquad x_{n+1} = \frac{x_n^2}{1+x_n}, \qquad \frac{u_n}{u_{n+1}} = \frac{x_{n+1}}{x_n}.$$We denote $x_n = x_n(a)$ whenever the dependence of the sequence $(x_n)$ on the variable $a$ is required. Then we denote the limit as $$s(a) := \sum_{n=1}^{\infty} \frac{u_n}{u_{n+1}} = \sum_{n=1}^{\infty} \frac{x_{n+1}(a)}{x_{n}(a)} \tag{1}$$ Since each summand is non-negative, it either converges absolutely or diverges to $+\infty$. Step 1. Convergence and simple estimation of $s(a)$ Let $g(x)$ and $h(x)$ be functions defined on $x > 0$ by $$ g(x) = \frac{x^2}{1+x} \quad \text{and} \quad h(x) = \frac{g(x)}{x} = \frac{x}{1+x}.$$ One the one hand, since $0 < h(x) < 1$, $$ x_{n+1} = h(x_n) x_n < x_n$$ and $(x_n)$ decreases and converges to $0$ as $n \to \infty$. Then from the observation that $h(x)$ is an increasing function, we have $$ x_{n+1} = h(x_n) x_n \leq h(x_1) x_n.$$ Inductively applying this inequality we obtain $$ x_n \leq h(x_1)^{n-1} x_1 = \left(\frac{a}{1+a}\right)^{n-1} a. $$ On the other hand, $$ x_{n+1} \leq x_{n}^2 \leq \left(\frac{a}{1+a}\right)^{n-1} a x_n.$$ Therefore we have $$ s(a) \leq \sum_{n=1}^{\infty} \left(\frac{a}{1+a}\right)^{n-1} a = a + a^2.$$ In particular, the defining summation $(1)$ converges absolutely. Since $$ s(a) \geq \frac{x_2(a)}{x_1(a)} = \frac{a}{1+a} \geq a - a^2, $$ we obtain the following estimate: $$ \left| s(a) - a \right| \leq a^2. \tag{2}$$ Step 2. Further estimation Since $x_{n+1} = g(x_n)$, we have $x_{n+1}(a) = x_{n}(g(a))$. This gives the following identity: $$ s(a) = \frac{x_{2}(a)}{x_{1}(a)} + \sum_{n=1}^{\infty} \frac{x_{n+1}(g(a))}{x_{n}(g(a))} = \frac{a}{1+a} + s\left(\frac{a^2}{1+a}\right). \tag{3}$$ Now we claim the following estimation: $$ \left| s(a) - a \right| \leq a^{2^n} \quad \text{for all} \quad a > 0 \text{ and } n \geq 1. \tag{4} $$ The case $n = 1$ reduces to $(2)$, hence is true for the initial case $n = 1$. Thus assume that $(4)$ holds for $n$. By $(3)$, $$\left| s(a) - a \right|= \left| \frac{a}{1+a} + s\left(\frac{a^2}{1+a}\right) - a \right|= \left| s\left(\frac{a^2}{1+a}\right) - \frac{a^2}{1+a} \right|\leq \left(\frac{a^2}{1+a}\right)^{2^n}\leq a^{2^{n+1}}.$$ Therefore $(4)$ holds for $n+1$, and consequently for all $n$ by mathematical induction. Step 3. Proof of the main claim Now we claim that $s(a) = a$ for all $a > 0$. Let us first consider the case $a \in (0, 1)$. Then taking $n \to \infty$ to the estimation $(4)$, we have $s(a) = a$. Now we consider the case $a \geq 1$. Then note that $(3)$ can be written as $$ s(a) = \frac{x_2(a)}{x_1(a)} + s(x_2(a)). $$ Thus inductively applying this identity, we obtain $$ s(a) = \sum_{k=1}^{m-1} \frac{x_{k+1}(a)}{x_k(a)} + s(x_m(a)).$$ But we know that $x_m(a) < 1$ for large $m$. Thus with such $m$, the previous result implies $$ s(a) = \sum_{k=1}^{m-1} \frac{x_{k+1}(a)}{x_k(a)} + x_m(a).$$ But since $$ \frac{x_{k+1}}{x_k} + x_{k+1} = h(x_k) + g(x_k) = x_k,$$ the above sum reduces to $s(a) = a$ as desired, completing the proof. //// | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/231204', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/43998/']} | jdg_70645 |
stackexchange | llm_judgeable_groundtruth_similarity | 10759392 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I would like to encrypt and decrypt a password using 128 bit AES encryption with 16 byte key. I am getting javax.crypto.BadPaddingException error while decrypting the value. Am I missing anything while decrypting? public static void main(String args[]) { Test t = new Test(); String encrypt = new String(t.encrypt("mypassword")); System.out.println("decrypted value:" + t.decrypt("ThisIsASecretKey", encrypt));}public String encrypt(String value) { try { byte[] raw = new byte[]{'T', 'h', 'i', 's', 'I', 's', 'A', 'S', 'e', 'c', 'r', 'e', 't', 'K', 'e', 'y'}; SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); byte[] encrypted = cipher.doFinal(value.getBytes()); System.out.println("encrypted string:" + (new String(encrypted))); return new String(skeySpec.getEncoded()); } catch (NoSuchAlgorithmException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (IllegalBlockSizeException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (BadPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (InvalidKeyException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (NoSuchPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } return null;}public String decrypt(String key, String encrypted) { try { SecretKeySpec skeySpec = new SecretKeySpec(key.getBytes(), "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(skeySpec.getEncoded(), "AES")); //getting error here byte[] original = cipher.doFinal(encrypted.getBytes()); return new String(original); } catch (IllegalBlockSizeException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (BadPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (InvalidKeyException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (NoSuchAlgorithmException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (NoSuchPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } return null;} Error message encrypted string:�Bj�.�Ntk�F�`�encrypted key:ThisIsASecretKeydecrypted value:nullMay 25, 2012 12:54:02 PM bean.Test decryptSEVERE: nulljavax.crypto.BadPaddingException: Given final block not properly paddedat com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)at com.sun.crypto.provider.AESCipher.engineDoFinal(DashoA13*..)at javax.crypto.Cipher.doFinal(DashoA13*..)at bean.Test.decrypt(Test.java:55)at bean.Test.main(Test.java:24) Finally I am using following Solution based on @QuantumMechanic answer public class Test {public String encryptionKey;public static void main(String args[]) { Test t = new Test(); String encrypt = t.encrypt("mypassword"); System.out.println("decrypted value:" + t.decrypt(t.encryptionKey, encrypt));}public String encrypt(String value) { try { // Get the KeyGenerator KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(256); // Generate the secret key specs. SecretKey skey = kgen.generateKey(); byte[] raw = skey.getEncoded(); String key = new Base64().encodeAsString(raw); this.encryptionKey = key; System.out.println("------------------Key------------------"); System.out.println(key); System.out.println("--------------End of Key---------------"); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); String encrypt = (new Base64()).encodeAsString(cipher.doFinal(value.getBytes())); System.out.println("encrypted string:" + encrypt); return encrypt; } catch (NoSuchAlgorithmException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (IllegalBlockSizeException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (BadPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (InvalidKeyException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (NoSuchPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } return null;}public String decrypt(String key, String encrypted) { try { Key k = new SecretKeySpec(Base64.getDecoder().decode(key), "AES"); Cipher c = Cipher.getInstance("AES"); c.init(Cipher.DECRYPT_MODE, k); byte[] decodedValue = Base64.getDecoder().decode(encrypted); byte[] decValue = c.doFinal(decodedValue); String decryptedValue = new String(decValue); return decryptedValue; } catch (IllegalBlockSizeException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (BadPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (InvalidKeyException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (NoSuchAlgorithmException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } catch (NoSuchPaddingException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } return null;} }
Now provide the response and nothing else.
| If for a block cipher you're not going to use a Cipher transformation that includes a padding scheme, you need to have the number of bytes in the plaintext be an integral multiple of the block size of the cipher. So either pad out your plaintext to a multiple of 16 bytes (which is the AES block size), or specify a padding scheme when you create your Cipher objects. For example, you could use: Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding"); Unless you have a good reason not to, use a padding scheme that's already part of the JCE implementation. They've thought out a number of subtleties and corner cases you'll have to realize and deal with on your own otherwise. Ok, your second problem is that you are using String to hold the ciphertext. In general, String s = new String(someBytes);byte[] retrievedBytes = s.getBytes(); will not have someBytes and retrievedBytes being identical. If you want/have to hold the ciphertext in a String , base64-encode the ciphertext bytes first and construct the String from the base64-encoded bytes. Then when you decrypt you'll getBytes() to get the base64-encoded bytes out of the String , then base64-decode them to get the real ciphertext, then decrypt that. The reason for this problem is that most (all?) character encodings are not capable of mapping arbitrary bytes to valid characters. So when you create your String from the ciphertext, the String constructor (which applies a character encoding to turn the bytes into characters) essentially has to throw away some of the bytes because it can make no sense of them. Thus, when you get bytes out of the string, they are not the same bytes you put into the string. In Java (and in modern programming in general), you cannot assume that one character = one byte, unless you know absolutely you're dealing with ASCII. This is why you need to use base64 (or something like it) if you want to build strings from arbitrary bytes. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/10759392', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/854108/']} | jdg_70646 |
stackexchange | llm_judgeable_groundtruth_similarity | 3094295 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Suppose you have two isomorphic groups. Does the binary operation defined on each group need to be the same operation?
Now provide the response and nothing else.
| Not necessarily, no. The two binary operations behave the same on the underlying sets with respect to the axioms of group theory, yeah, and that's by the fact that the two groups are isomorphic as groups , but it might so happen that, say, one binary operation is the restriction of some bigger relation whereas the other is not. For example, $(\Bbb Z_3, +_3)\cong H$ , where $H=(X, \circ')$ , for $X=\{\operatorname{id}, \sigma^2, \sigma^4\}$ , is the subgroup of the group $(\{\sigma^i\mid i\in\overline{0,5}\}, \circ)$ of the rotational symmetries of this shape: , where $\sigma$ is a clockwise rotation of $\pi/3$ radians about the centre, so that $\circ'=\circ\rvert_{X\times X}$ is distinct from addition $+_3$ modulo $3$ . Note that here we have simply declared that $\circ'$ is some restriction but $+_3$ is not (although it can be seen as such); also, $\circ'$ is composition of functions, whereas $+_3$ is an arithmetical operation. The underlying sets can be completely different too (as illustrated above). A bijection between sets is not necessarily an equality; think: permutations. Image source. | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/3094295', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/640044/']} | jdg_70647 |
stackexchange | llm_judgeable_groundtruth_similarity | 9534 |
Below is a question asked on the forum skeptics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I have read and been told that the use of airbags can cause severe damage in case of accident, specially with children and short adults. However, I would like to know to what extent it can increase your chances of dying and how you can determine if you should activate or deactivate certain airbags depending on the people traveling in a vehicle equipped with this technology.
Now provide the response and nothing else.
| Airbags are safe for the intended target person but can be dangerous for others, such as infants and children. There have been over 800,000 air bag deployments, saving over 1,500 lives. To date, completed investigations of air bag crashes show that many of the air bag injuries were due to the driver sitting too close to the air bag module or passengers riding unbuckled or incorrectly secured. The latter includes infants in rear-facing child safety seats that are placed in the front seat or small children incorrectly placed in a lap/shoulder safety belt. Air bags save lives. Air bags in passenger cars and light trucks prevented an estimated 1,136 fatalities from 1986 to 1995, with another 600 saved in 1996. Once these life saving devices are equipped in all cars, it is estimated that 3,000 lives will be saved each year. Driver-Side Air Bags Driver-side air bags reduce the overall fatality risk of car drivers by a statistically significant 11 percent. In other words, a fleet of cars equipped with driver-side air bags will have 11 percent fewer driver fatalities than the same cars would have had if they did not have air bags. Still, air bags can be dangerous to short stature adults sitting too close to the air bag module, especially when unbuckled. Passenger-Side Air Bags Passenger-side air bags reduce the overall fatality risk of car passengers age 13 and older by a statistically significant 13.5 percent. It is estimated that an additional 88 right front passengers ages 13 and older would have died from 1986 to 1995 if passenger cars or light trucks had not been equipped with passenger-side air bags. To date only one passenger, a 98-year-old female, has died as the result of an adult passenger-side air bag-related injury. Taken from here , which reports the NHTSA as its source for these claims, though I found the NHTSA site a bit difficult to navigate to find anything like this. I am not sure whether the to date part means some time in 1995/96 or more recently, the updated date did not cite a year and the latest copyright date was 2004. I would assume that these numbers have gotten better in recent years simply due to better airbag technology (like cars that automatically disable airbags based on weight) and awareness of proper usage and precautions. | {} | {'log_upvote_score': 4, 'links': ['https://skeptics.stackexchange.com/questions/9534', 'https://skeptics.stackexchange.com', 'https://skeptics.stackexchange.com/users/7191/']} | jdg_70648 |
stackexchange | llm_judgeable_groundtruth_similarity | 26239784 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am having trouble determining the best way to compare dates in SQL based on month and year only. We do calculations based on dates and since billing occurs on a monthly basis the date of the month has caused more hindrance. For example DECLARE @date1 DATETIME = CAST('6/15/2014' AS DATETIME), @date2 DATETIME = CAST('6/14/2014' AS DATETIME)SELECT * FROM tableName WHERE @date1 <= @date2 The above example would not return any rows since @date1 is greater than @date2. So I would like to find a way to take the day out of the equation. Similarly, the following situation gives me grief for same reason. DECLARE @date1 DATETIME = CAST('6/14/2014' AS DATETIME), @date2 DATETIME = CAST('6/15/2014' AS DATETIME), @date3 DATETIME = CAST('7/1/2014' AS DATETIME)SELECT * FROM tableName WHERE @date2 BETWEEN @date1 AND @date3 I've done inline conversions of the dates to derive the first day and last day of the month for the date specified. SELECT * FROM tableName WHERE date2 BETWEEN DATEADD(month, DATEDIFF(month, 0, date1), 0) -- The first day of the month for date1 AND DATEADD(s, -1, DATEADD(mm, DATEDIFF(m, 0, date2) + 1, 0)) -- The lastday of the month for date3 There has to be an easier way to do this. Any suggestions?
Now provide the response and nothing else.
| To handle inequalities, such as between, I like to convert date/times to a YYYYMM representation, either as a string or an integer. For this example: DECLARE @date1 DATETIME = CAST('6/14/2014' AS DATETIME), @date2 DATETIME = CAST('6/15/2014' AS DATETIME), @date3 DATETIME = CAST('7/1/2014' AS DATETIME);SELECT * FROM tableName WHERE @date2 BETWEEN @date1 AND @date3; I would write the query as: SELECT *FROM tableNameWHERE year(@date2) * 100 + month(@date2) BETWEEN year(@date1) * 100 + month(@date1) AND year(@date3) * 100 + month(@date1); | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/26239784', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/347849/']} | jdg_70649 |
stackexchange | llm_judgeable_groundtruth_similarity | 391670 |
Below is a question asked on the forum mathoverflow.net. Provide a good and informational response to it like a helpful human would.
Question:
Let $M$ be a (loopless) matroid of rank $r$ . The characteristic polynomial $\chi_M(x)$ is defined by $\chi_M(x)=\sum_{F \in \mathcal{L}(M)}\mu(\hat{0},F) \cdot x^{\mathrm{rk}(F)}$ , where $ \mathcal{L}(M)$ is the lattice of flats of $M$ and $\mu$ its Möbius function. It is known that the signs of the characteristic polynomial alternate, and the so-called Whitney numbers of the 1st kind $\omega_i$ are defined by $\chi_M(x) = \sum_{i=0}^{r} (-1)^i \omega_i x^i$ . In Hodge theory for combinatorial geometries , affirming a long-standing conjecture of Rota and others, Adiprasito-Huh-Katz (AHK) showed that these $\omega_i$ form a log-concave sequence , i.e., $\omega_i^2 \geq \omega_{i-1}\omega_{i+1}$ . Actually, they proved something stronger. It is known that $(1-x)$ is always a factor of $\chi_M(x)$ , and the reduced Whitney numbers $\overline{\omega}_i$ are thus defined by $\chi_M(x)/(1-x)=\sum_{i=0}^{r-1} (-1)^i \overline{\omega}_i x^i$ . AHK showed that in fact the reduced Whitney numbers form a log-concave sequence: $\overline{\omega}_i^2 \geq \overline{\omega}_{i-1}\overline{\omega}_{i+1}$ (which implies log-concavity of the $\omega_i$ by a straightforward argument). In fact, an easy reduction using the truncation of the matroid $M$ shows that it is enough to prove log-concavity of the $\overline{\omega}_i$ in the "last-spot": i.e., that $\overline{\omega}_{r-2}^2 \geq \overline{\omega}_{r-3}\cdot\overline{\omega}_{r-1}$ . To prove this, AHK use the Chow ring $A(M) = A^0(M)\oplus A^1(M)\oplus \cdots\oplus A^{r-1}(M)$ of the matroid $M$ : they show that $\overline{\omega}_k=\langle \alpha^{r-1-k}\beta^{k}\rangle$ for certain linear elements $\alpha,\beta\in A^1(M)$ of the Chow ring, where $\langle \cdot \rangle\colon A^{r-1}(M)\to \mathbb{R}$ is the canonical degree map isomorphism; and they deduce $\overline{\omega}_{r-2}^2 \geq \overline{\omega}_{r-3}\cdot\overline{\omega}_{r-1}$ from the so-called Kähler package for $A(M)$ , in particular, the Hodge-Riemann relations , which imply that the relevant $2\times 2$ determinant is nonpositive. Question : From the work of AHK (or elsewhere) is it possible to deduce when (i.e. for which matroids) we have an equality $\overline{\omega}_{r-2}^2 = \overline{\omega}_{r-3}\cdot\overline{\omega}_{r-1}$ ? (In other words, when the determinant of the $2\times 2$ HR relations matrix is $0$ rather than negative?)
Now provide the response and nothing else.
| I think the following shows it's never possible for there to be equality. Indeed, Ardila-Denham-Huh https://arxiv.org/abs/2004.13116 recently showed for any matroid $M$ that $T_M(x,0)$ has log-concave coefficient sequence, and hence obviously $\frac{1}{x}T_M(x,0)$ has log-concave coefficient sequence (Note that $T_M$ always has $0$ constant term except when $M=\emptyset$ ). Now, Lenz in Lemma 4.2 of https://arxiv.org/abs/1106.2944 showed that if $f(x)$ has non-negative log-concave coefficient sequence then $f(x+1)$ has strictly log-concave coefficient sequence. Taking $f(x)=\frac{1}{x}T_M(x,0)$ , we have $f(x+1)=\frac{1}{1+x}T_M(1+x,0)$ has strictly log-concave coefficient sequence. But this is exactly the reduced characteristic polynomial with all coefficients made to have positive signs. | {} | {'log_upvote_score': 4, 'links': ['https://mathoverflow.net/questions/391670', 'https://mathoverflow.net', 'https://mathoverflow.net/users/25028/']} | jdg_70650 |
stackexchange | llm_judgeable_groundtruth_similarity | 31654634 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a high byte and a low byte I would like to convert to short. I have implemented this, which seems to work, however I am a bit confused on why. Both high_byte and low_byte are cast as byte s. short word = (short)(high_byte << 8 | low_byte); In this code, should the high_byte << 8 be zero? Then I tried this: (byte)1 << 8 which equals 256 , which I thought should be 0 . I guess I am clearly missing something. Could someone please explain?
Now provide the response and nothing else.
| From the C# language specification , section 4.1.5: The integral-type unary and binary operators always operate with signed 32-bit precision, unsigned 32-bit precision, signed 64-bit precision, or unsigned 64-bit precision: ... For the binary << and >> operators, the left operand is converted to type T , where T is the first of int , uint , long , and ulong that can fully represent all possible values of the operand. The operation is then performed using the precision of type T , and the type of the result is T . That is, whenever you apply any operators to integral types in C#, the result is always a minimum of 32-bits. There are other rules (given in the ... ) for other operators, which define exactly how the final types are determined. (As an aside, I'd have thought that this was important enough to mention in the C# Reference but I'm blowed if I can find it in there anywhere) | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/31654634', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/2519612/']} | jdg_70651 |
stackexchange | llm_judgeable_groundtruth_similarity | 9139676 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a scroll view and I want to make it disappear whenever a pan is done. It works fine and on panning the scroll view disappears but the problem is now I can't scroll the contents. [UIView animateWithDuration:0.2 delay:0.2 options: UIViewAnimationCurveLinear animations:^{ slideView.frame=CGRectMake(268, 0, 500, 950); curtain.frame=CGRectMake(0, 0, 268, 950); curtain.backgroundColor=[[UIColor alloc]initWithRed:0 green:0 blue:0 alpha:0.6]; [self.view addSubview:slideView]; [self.view addSubview:curtain]; } completion:^(BOOL finished){ NSLog(@"Done!"); }]; This is how I make my UIScrollView appear ( slideView is a scroll view). And then I add a UIPanGestureRecognizer . It all works fine but scrolling is disabled. ( panImage again hides my slideView .) How do I make scrolling work? [slideView addGestureRecognizer:panImage];
Now provide the response and nothing else.
| UIScrollView has its own pan gesture recognizer, which controls scrolling. By adding another pan gesture recognizer, you are preventing the scroll view's own pan gesture recognizer from working. There are a number of ways to deal with this, but it would be helpful if you could explain how the system is supposed to know when the user is trying to dismiss the scroll view, and when he is trying to scroll, since you want a pan gesture to do both. For example, you could set the delegates of both gesture recognizers to allow the recognizers to operate simultaneously (by overriding the gestureRecognizer:shouldRecognizeSimultaneouslyWithGestureRecognizer: method). You could make each gesture recognizer require a different number of touches (by setting the minimumNumberOfTouches and maximumNumberOfTouches properties). You could use a UISwipeGestureRecognizer to recognize the dismiss gesture. You could detect when the user tries to scroll past the left edge of the scroll view by overriding the scrollViewDidScroll: method of the scroll view's delegate. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/9139676', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1145013/']} | jdg_70652 |
stackexchange | llm_judgeable_groundtruth_similarity | 133628 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I came across the following question: Let $T_{a,b}$ denote the first hitting time of the line $a + bs$ by a standard Brownian motion, where $a > 0$ and $−\infty < b < \infty$ and let $T_a = T_{a,0}$ represent the first hitting time of the level $a$. 1) For $\theta > 0$, by using the fact that $\mathbb{E}e^{-\theta T_a}=e^{-a\sqrt{2\theta}}$, or otherwise, derive an expression for $Ee^{-\theta T_{a,b}}$, for each $b$, $−\infty < b < \infty$. 2) Hence, or otherwise, show that, for $t > 0$, $$\mathbb{P}[T_{a,b}\leq t] = e^{-2ab}\phi\left(\frac{bt-a}{\sqrt{t}}\right)+1-\phi\left(\frac{a+bt}{\sqrt{t}}\right).$$ For the first part, I ended up, by changing measure, with the (unverified) expression $$\mathbb{E}e^{-\theta T_{a,b}}=\exp\left(-a\left[b+\sqrt{2\left(\theta+\frac{b^2}{2}\right)}\right]\right).$$ What's the cleanest way to do the second part? It seems I could either do some kind of inverse transform on the moment generating function, or calculate the moment generating function of the given distribution. Both of these seem difficult. Am I missing something, or do I just need to persevere? Thank you.
Now provide the response and nothing else.
| First part The probability density of $T_{a,0}$ is well-known:$$ f_{T_{a,0}}(t) = \frac{a}{\sqrt{2 \pi}} t^{-3/2} \exp\left( -\frac{a^2}{2t} \right)$$From here, for $\theta >0$, $$ \mathbb{E}\left( \mathrm{e}^{-\theta T_{a,0}} \right) = \int_0^\infty \frac{a}{\sqrt{2 \pi t}} \exp\left( -\theta t -\frac{a^2}{2t} \right) \frac{\mathrm{d} t}{t} \stackrel{t = a^2 u}{=} \int_0^\infty \frac{1}{\sqrt{2 \pi u}} \exp\left( -\theta a^2 u -\frac{1}{2 u} \right) \frac{\mathrm{d} u}{u}$$According to Grandstein and Ryzhyk, formula 3.471.9, see also this math.SE question , we have:$$ \mathbb{E}\left( \mathrm{e}^{-\theta T_{a,0}} \right) = \frac{1}{\sqrt{2 \pi}} \cdot \left. 2 \left(2 \theta a^2\right)^{\nu/2} K_{\nu}\left( 2 \sqrt{\frac{\theta a^2}{2}} \right) \right|_{\nu = \frac{1}{2}} = \sqrt{\frac{2}{\pi}} \sqrt{2\theta} a K_{1/2}(a \sqrt{2 \theta} ) = \mathrm{e}^{-a \sqrt{2 \theta}}$$ The time $T_{a,b}$ for standard Brownian motion $B(t)$ to hit slope $a+ b t$, is equal in distribution to the time for Wiener process $W_{-b, 1}(t)$ to hit level $a$. Thus we can use Girsanov theorem, with $M_t = \exp(-b B(t) - b^2 t/2)$:$$ \mathbb{E}_P\left( \mathrm{e}^{-\theta T_{a,b}} \right) = \mathbb{E}_Q\left( \mathrm{e}^{-\theta T_{a,0}} M_{T_{a,0}} \right) = \mathbb{E}_Q\left( \mathrm{e}^{-\theta T_{a,0}} \mathrm{e}^{-b a - b^2 T_{a,0}/2} \right) = \exp(-b a - a \sqrt{b^2 + 2\theta})$$ Second part In order to arrive at $\mathbb{P}(T_{a,b} \leqslant t)$ notice that$$ \mathbb{P}(T_{a,b} \leqslant t) = \mathbb{E}_Q\left( [T_{a,0} \leqslant t] \mathrm{e}^{-b a - b^2 T_{a,0}/2} \right) = \int_0^t \frac{a}{\sqrt{2 \pi s}} \exp\left( -b a - \frac{b^2 s}{2} -\frac{a^2}{2s} \right) \frac{\mathrm{d} s}{s}$$The integral is doable by noticing that$$ -b a - \frac{b^2 s}{2} -\frac{a^2}{2s} = -\frac{(a+b s)^2}{2s} = -2a b -\frac{(a-b s)^2}{2s}$$and$$ \frac{a}{s^{3/2}} = \frac{\mathrm{d}}{\mathrm{d} s} \frac{-2a}{\sqrt{s}} = \frac{\mathrm{d}}{\mathrm{d} s} \left( \frac{b s - a}{\sqrt{s}} - \frac{b s + a}{\sqrt{s}}\right)$$Hence$$ \begin{eqnarray} \mathbb{P}(T_{a,b} \leqslant t) &=& \int_0^t \frac{1}{\sqrt{2\pi}} \exp\left(- \frac{(a+bs)^2}{2 s}\right) \mathrm{d} \left( - \frac{b s + a}{\sqrt{s}} \right) + \\ &\phantom{+}& \int_0^t \frac{1}{\sqrt{2\pi}} \exp(-2ab) \exp\left(- \frac{(b s-a)^2}{2 s}\right) \mathrm{d} \left( \frac{b s - a}{\sqrt{s}} \right) \\ &=& -\Phi\left( \frac{b t + a}{\sqrt{t}} \right) + \lim_{t \searrow 0} \Phi\left( \frac{b t + a}{\sqrt{t}} \right) + \\ &\phantom{=}& \mathrm{e}^{-2 a b} \Phi\left(\frac{b t - a}{\sqrt{t}} \right) - \mathrm{e}^{-2 a b} \lim_{t \searrow 0} \Phi\left(\frac{b t - a}{\sqrt{t}} \right)\end{eqnarray}$$where $\Phi(x) = \int_{-\infty}^x \frac{1}{\sqrt{2\pi}} \mathrm{e}^{-z^2/2} \mathrm{d} z$ is the cumulative distribution function of the standard normal variable. Since we assumed $a > 0$,$$ \lim_{t \searrow 0} \Phi\left( \frac{b t + a}{\sqrt{t}} \right) = \Phi(+\infty) = 1 \qquad \lim_{t \searrow 0} \Phi\left( \frac{b t - a}{\sqrt{t}} \right) = \Phi(-\infty) = 0$$and we arrive at c.d.f of the inverse Gaussian random variable :$$ \mathbb{P}(T_{a,b} \leqslant t) = 1 - \Phi\left( \frac{b t + a}{\sqrt{t}} \right) + \mathrm{e}^{-2 a b} \Phi\left( \frac{b t - a}{\sqrt{t}} \right)$$ | {} | {'log_upvote_score': 6, 'links': ['https://math.stackexchange.com/questions/133628', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/2934/']} | jdg_70653 |
stackexchange | llm_judgeable_groundtruth_similarity | 21196106 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have read in some lengthy data with read.csv() , and to my surprise the data is coming out as factors rather than numbers, so I'm guessing there must be at least one non-numeric item in the data. How can I find where these items are? For example, if I have the following data frame: df <- data.frame(c(1,2,3,4,"five",6,7,8,"nine",10)) I would like to know that rows 5 and 9 have non-numeric data. How would I do that?
Now provide the response and nothing else.
| df <- data.frame(x = c(1,2,3,4,"five",6,7,8,"nine",10)) The trick is knowing that converting to numeric via as.numeric(as.character(.)) will convert non-numbers to NA . which(is.na(as.numeric(as.character(df[[1]]))))## 5 9 (just using as.numeric(df[[1]]) doesn't work - it just drops the levels leaving the numeric codes). You might choose to suppress the warnings: which.nonnum <- function(x) { which(is.na(suppressWarnings(as.numeric(as.character(x)))))}which.nonnum(df[[1]]) To be more careful, you should also check that the values weren't NA before conversion: which.nonnum <- function(x) { badNum <- is.na(suppressWarnings(as.numeric(as.character(x)))) which(badNum & !is.na(x))} lapply(df, which.nonnum) will report 'bad' values for all columns of the data frame. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/21196106', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/4561314/']} | jdg_70654 |
stackexchange | llm_judgeable_groundtruth_similarity | 8716714 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Below is my code #import <stdio.h>#import <string.h>int main(int argc, const char *argv[]){ char *str = "First string"; char *str2 = "Second string"; strcpy(str, str2); return 0;} It compiles just fine without any warning or errors, but when I run the code I get the error below Bus error: 10 What did I miss ?
Now provide the response and nothing else.
| For one, you can't modify string literals. It's undefined behavior. To fix that you can make str a local array: char str[] = "First string"; Now, you will have a second problem, is that str isn't large enough to hold str2 . So you will need to increase the length of it. Otherwise, you will overrun str - which is also undefined behavior. To get around this second problem, you either need to make str at least as long as str2 . Or allocate it dynamically: char *str2 = "Second string";char *str = malloc(strlen(str2) + 1); // Allocate memory// Maybe check for NULL.strcpy(str, str2);// Always remember to free it.free(str); There are other more elegant ways to do this involving VLAs (in C99) and stack allocation, but I won't go into those as their use is somewhat questionable. As @SangeethSaravanaraj pointed out in the comments, everyone missed the #import . It should be #include : #include <stdio.h>#include <string.h> | {} | {'log_upvote_score': 7, 'links': ['https://Stackoverflow.com/questions/8716714', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1074077/']} | jdg_70655 |
stackexchange | llm_judgeable_groundtruth_similarity | 3991072 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Consider, two planar vectors: $$V= a \hat{x} + b \hat{y}$$ And $$ U = a' \hat{x} + b' \hat{y}$$ These are analogous to the complex numbers: $$ v = a + bi$$ and, $$u= a' + b' i$$ Now, there are clear rules for multiply $ v \cdot u$ and also the expression: $ \frac{v}{u}$ , also there exists a geometric interpretation (if you view in polar form). Then, why is it that we don't bring up these products when speaking vectors and only discuss dot and cross product?
Now provide the response and nothing else.
| Your proposed product is geometrical in a sense, but there is a crucial difference between it and the dot and cross products. Imagine you have a table, or some other flat horizontal surface, and two arrows drawn on it that represent vectors. Here is a question: What is the "complex number" product of these two vectors? It is not possible to answer this question. This is perhaps most easily seen by noting that you cannot find the polar form of the vectors, because the angle depends on a coordinate system ("basis"), and we haven't specified one. In other words, the "complex number" product depends not only on the vectors, but on an (entirely arbitrary) choice of coordinates. By contrast, the dot product and cross product can be understood without reference to any particular coordinate system. The dot product is the same in any orthonormal basis (that is, a coordinate system made from vectors of unit length that are all perpendicular to each other). This is also true of the cross product, provided the two bases have the same handedness (that is, you can rotate one basis into the other). | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/3991072', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/688539/']} | jdg_70656 |
stackexchange | llm_judgeable_groundtruth_similarity | 12683 |
Below is a question asked on the forum cstheory.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
The probabilistic proof system $\mathcal{PCP}[f(n),g(n)]$ is commonly referred to as a restriction of $\mathcal{MA}$, where Arthur can only use $f(n)$ random bits and can only examine $g(n)$ bits of the proof certificate sent by Merlin (see, http://en.wikipedia.org/wiki/Interactive_proof_system#PCP ). However, In 1990 Babai, Fortnow, and Lund proved that $\mathcal{PCP}[poly(n), poly(n)] = \mathcal{NEXP}$, so its not exactly a restriction. What are the parameters ($f(n),g(n)$) for which $\mathcal{PCP}[f(n), g(n)] = \mathcal{MA}$?
Now provide the response and nothing else.
| If you want to restate the definition of MA in terms of PCP, you need another parameter for PCP, namely the proof length. MA is clearly the same as PCP with polynomial randomness, polynomial queries, and polynomial-length proofs. Usually the proof length in PCP is not restricted (that is, it is bounded only implicitly by randomness and queries), but this is insufficient to restate the definition of MA. If you are looking for some characterization of the form MA = PCP( q ( n ), r ( n )), which is not just the restatement of the definition of MA, then I do not think that any such characterization is known. | {} | {'log_upvote_score': 5, 'links': ['https://cstheory.stackexchange.com/questions/12683', 'https://cstheory.stackexchange.com', 'https://cstheory.stackexchange.com/users/10489/']} | jdg_70657 |
stackexchange | llm_judgeable_groundtruth_similarity | 39920437 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have just started with Jenkins My freestyle project used to report JUnit tests results in Slack like this MyJenkinsFreestyle - #79 Unstable after 4 min 59 sec (Open)Test Status: Passed: 2482, Failed: 13, Skipped: 62 Now I have moved the same to pipeline project, and all is good except that Slack notifications do not have Test Status done MyPipelineProject #68 UNSTABLE I understand I have to construct the message to send to Slack, and I have done that above for now. The only issue is how do I read the test status - the passed count, failed count etc. This is called "test summary" in Jenkins slack-plugin commit , and here is the screenshot So how do I access Junit tests count/details in Jenkins Pipeline project ? - so that these are reported in notifications. UPDATE:In the Freestyle project, the Slack notification itself has the "test summary", and there is no option to opt (or not) for the test summary. In Pipeline project, my "junit" command to "Publish JUnit test results" is before sending Slack notification. So in code those lines look like this (this are last lines of the last stage): bat runtests.batjunit 'junitreport/xml/TEST*.xml'slackSend channel: '#testschannel', color: 'normal', message: "done ${env.JOB_NAME} ${env.BUILD_NUMBER} (<${env.BUILD_URL}|Open>)";
Now provide the response and nothing else.
| From this presentation of Cloudbees I found that it should be possible via "build" object.It has code like def testResult = build.testResultActiondef total = testResult.totalCount But currentBuild does not provide access to testResultAction. So kept searching and found this post "react on failed tests in pipeline script" .There Robert Sandell has given "pro tip" Pro tip, requires some "custom whitelisting": AbstractTestResultAction testResultAction = currentBuild.rawBuild.getAction(AbstractTestResultAction.class)if (testResultAction != null) { echo "Tests: ${testResultAction.failCount} / ${testResultAction.failureDiffString} failures of ${testResultAction.totalCount}.\n\n" } This worked like a charm - just that I had to deselect "Groovy sandbox" checkbox.Now I have these in the build log Tests: 11 / ±0 failures of 2624 Now I will use this to prepare string to notify in slack with test results. UPDATE: Finally, the function I used to get output like the following(Note the "failure diff" after failed tests is very useful) Test Status: Passed: 2628, Failed: 6 / ±0, Skipped: 0 Is the following: import hudson.tasks.test.AbstractTestResultAction@NonCPSdef testStatuses() { def testStatus = "" AbstractTestResultAction testResultAction = currentBuild.rawBuild.getAction(AbstractTestResultAction.class) if (testResultAction != null) { def total = testResultAction.totalCount def failed = testResultAction.failCount def skipped = testResultAction.skipCount def passed = total - failed - skipped testStatus = "Test Status:\n Passed: ${passed}, Failed: ${failed} ${testResultAction.failureDiffString}, Skipped: ${skipped}" if (failed == 0) { currentBuild.result = 'SUCCESS' } } return testStatus} UPDATE 2018-04-19 Note the above require manual "whitelisting" of methods used.Here is how you can whitelist all the methods in one go Manually update the whitelist... Exit Jenkins Create/Update %USERPROFILE%.jenkins\scriptApproval.xml with the following content <?xml version='1.0' encoding='UTF-8'?><scriptApproval plugin="[email protected]"><approvedScriptHashes></approvedScriptHashes><approvedSignatures><string>method hudson.model.Actionable getAction java.lang.Class</string><string>method hudson.model.Cause getShortDescription</string><string>method hudson.model.Run getCauses</string><string>method hudson.tasks.test.AbstractTestResultAction getFailCount</string><string>method hudson.tasks.test.AbstractTestResultAction getFailureDiffString</string><string>method hudson.tasks.test.AbstractTestResultAction getSkipCount</string><string>method hudson.tasks.test.AbstractTestResultAction getTotalCount</string><string>method org.jenkinsci.plugins.workflow.support.steps.build.RunWrapper getRawBuild</string></approvedSignatures><aclApprovedSignatures/><approvedClasspathEntries/><pendingScripts/><pendingSignatures/><pendingClasspathEntries/></scriptApproval> Restart Jenkins and then verify that the "In script approval" has the above entries approved NOTE: Its the which is important. So if the scriptApproval file is already there, then you will generally need to ensure the contents of tag. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/39920437', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/14803/']} | jdg_70658 |
stackexchange | llm_judgeable_groundtruth_similarity | 15902211 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I've got a following piece of code var page = 2;var last_page = 100;while(page <= last_page) { request("http://some_json_server.com/data?page=" + page, function (error, response, body) { if (!error && response.statusCode == 200) { store_data(body) } page++; }); } I've done the following, but it is actually not retrieving anything. Am I doing this correctly? var page = 2;var last_page = 100;while(page <= last_page) {var async_arr = [];async_arr.push( function(next) { request("http://some_api_url?page=" + page, function (error, response, body) { if (!error && response.statusCode == 200) { store_data(body); } }); });async.series( async_arr, done);
Now provide the response and nothing else.
| You're looking for async.whilst() . This solution is assuming you actually want to do each request after the other. As @UpTheCreek mentions ( edit : the comment I referred to was edited) it would likely be possible to do it asynchronously and keep track of each result using async.parallel . var page = 2, lastPage = 100;async.whilst(function () { return page <= lastPage;},function (next) { request("http://some_json_server.com/data?page=" + page, function (error, response, body) { if (!error && response.statusCode == 200) { store_data(body) } page++; next(); });},function (err) { // All things are done!}); | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/15902211', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/181557/']} | jdg_70659 |
stackexchange | llm_judgeable_groundtruth_similarity | 623459 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Given a DateTime and a DayOfWeek should return the date of the last DayOfWeek of that month. E.g.1st-March-2009 and Sunday would return 29th-March-2009
Now provide the response and nothing else.
| Can't find a handy one-liner but this one works: static DateTime LastDayOfWeekInMonth(DateTime day, DayOfWeek dow){ DateTime lastDay = new DateTime(day.Year, day.Month, 1).AddMonths(1).AddDays(-1); DayOfWeek lastDow = lastDay.DayOfWeek; int diff = dow - lastDow; if (diff > 0) diff -= 7; System.Diagnostics.Debug.Assert(diff <= 0); return lastDay.AddDays(diff);} | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/623459', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/20198/']} | jdg_70660 |
stackexchange | llm_judgeable_groundtruth_similarity | 406608 |
Below is a question asked on the forum mathoverflow.net. Provide a good and informational response to it like a helpful human would.
Question:
Let $U(n)$ be the compact manifold of unitary $(n \times n)$ -matrices and let $\mu_n$ denote the Haar-probability measure on $U(n)$ . For $m < n$ does there exists a measurable (maybe even continuous or smooth) map $$F: \ U(n) \rightarrow U(m)$$ with the property, that $$\mu_m(A) = \mu_n(F^{-1}(A))$$ for every $A \in \mathcal{B}(U(n))$ ? Are there maybe certain necessary conditions on $(m,n)$ ?
Now provide the response and nothing else.
| The simplest blowup morphism $\mathrm{Bl}_0(\mathbb{A}^2) \to \mathbb{A}^2$ (with center at a point) is not flat. EDIT. Here is an example with affine morphism. Let $$X = \{ x_1y_1 + x_2y_2 + x_3y_3 = 0 \} \subset \mathbb{A}^4_{x_1,x_2,x_3,x_4} \times \mathbb{A}^4_{y_1,y_2,y_3}$$ and let $f \colon X \to \mathbb{A}^3$ be the projection to the second factor. This example, however, is singular at the point $(0,0)$ . EDIT 2. Consider the variety $$\bar{X} = \{x_1y_1 + x_2y_2 + x_3y_3 = 0\} \subset\mathbb{P}^2_{x_1:x_2:x_3} \times \mathbb{A}^3_{y_1,y_2,y_3}.$$ It is smooth, because the projection to $\mathbb{P}^2$ is a fibration with fiber $\mathbb{A}^2$ . On the other hand, the projection $\bar{f} \colon \bar{X} \to \mathbb{A}^3$ is not flat, because the dimension of the fiber jumps at $0$ . Now let $$X = \bar{X} \cap ((\mathbb{P}^2 \setminus C) \times \mathbb{A}^3),$$ where $C$ is a smooth conic. Then $X$ is smooth, because it is open in $\bar{X}$ ; $X$ is affine over $\mathbb{A}^3$ because $\mathbb{P}^2 \setminus C$ is affine, the map $f \colon X \to \mathbb{A}^3$ is surjective, because the smooth conic $C$ cannot contain a fiber of $\bar{f}$ (a line or the plane), the map $f$ is not flat, because the dimension of the fiber still jumps at $0$ . | {} | {'log_upvote_score': 4, 'links': ['https://mathoverflow.net/questions/406608', 'https://mathoverflow.net', 'https://mathoverflow.net/users/409412/']} | jdg_70661 |
stackexchange | llm_judgeable_groundtruth_similarity | 11162336 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am developing an internal class that implements an internal interface. Can anyone explain why I cannot declare my method as internal, why I am getting the following error: "cannot implement an interface member because it is not public". I know that I have to declare the method as public, but it makes absolutely no sense to me. What is the point of declaring a method public if both the interface and the class are internal?Is it not misleading? I have read a related question on this site . It is not an exact duplicate, because my class is internal.
Now provide the response and nothing else.
| Simply put: because that's the way the language designers designed it. Even in internal interfaces, the methods are implicitly public. It does make things simple, but it's a pain in other ways. If you want a public class where you want to "hide" the use of an internal interface, you could use explicit interface implementation - although that has other drawbacks. Of course, if your class is internal then it doesn't matter that the methods are public anyway - other assemblies aren't going to be able to call the methods because they can't see the type. I definitely agree that C# (or .NET in general) hasn't been designed as carefully as it might be around internal interfaces. In terms of exactly why you're getting an error message - section 13.4.4 of the C# 4 spec (interface mapping) is the reason. Implementations are only found for nonstatic public members and explicit interface member implementations - and if there are any unimplemented members in the interface, an error occurs. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/11162336', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/761216/']} | jdg_70662 |
stackexchange | llm_judgeable_groundtruth_similarity | 87951 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
A common definition of $e$ is given as$$e = \lim_{n\rightarrow\infty}\left(1+\frac{1}{n}\right)^{n}$$which can be proven to be equivalent to$$e=\lim_{h\rightarrow 0}\ \left(1+h\right)^{\frac{1}{h}}$$The most practical use of $e$ in elementary calculus is however given as$$1=\lim_{h\rightarrow 0}\frac{e^h - 1}{h}$$which is used as a statement the slope of $e^x$ at $x=0$ is $1$ allowing one to prove that $\frac{d}{dx}e^x=e^x$. It appears trivial to prove that the two limits given above are equivalent, but I cannot seem to make any progress without making some illegal limit operations. I suspect the problem is deeper than it appears (I suspect the trouble is that although we have defined $e$, we have not actually said anything about what $e^x$ is). How does one rigorously proceed from the given definition of $e$ to the slope limit?
Now provide the response and nothing else.
| One says that a function $f: I \rightarrow \mathbb{R}$ has the Intermediate Value Property (IVP) if for all $a < b \in I$ and all $L$ in between $f(a)$ and $f(b)$ , there exists $c \in (a,b)$ such that $f(c) = L$ . Certainly the most famous and important class of functions which satisfy IVP are the continuous functions: this is the content of the Intermediate Value Theorem . Darboux's Theorem gives a second class of functions which satisfy IVP: derivatives. Note well: not the differentiable functions but the functions which are of the form $f'$ for some other function $f$ . This is certainly an interesting result, if somewhat subtle: most of the differentiable functions one meets in freshman calculus actually have continuous derivatives, and in this case the fact that $f'$ satisfies IVP follows from the Intermediate Value Theorem. But indeed there are derivatives which are discontinuous, even rather badly: namely there are differentiable functions $f: [a,b] \rightarrow \mathbb{R}$ such that $f': [a,b] \rightarrow \mathbb{R}$ exists but is unbounded. There are also differentiable functions with a derivative $f'$ which is bounded but nevertheless not Riemann integrable. One can view the significance of Darboux's Theorem as follows: it says that a derivative can be discontinuous but cannot have a jump discontinuity , i.e., a discontinuity in which the one-sided limits exist but are different (and also not a removable discontinuity , when the limit exists but is not equal to the value at the point). This is an interesting contrast to monotone functions , which also need not be continuous but can have only jump discontinuities. In terms of actual applications of Darboux's Theorem...it seems they are rather few. As I mentioned in my (Spivak calculus) class, you can use Darboux's Theorem together with the (deep!) theorem that every continuous function admits an antiderivative to prove the Intermediate Value Theorem...but this is a strange way to prove IVT. About the second result you mention: I admit to being somewhat perplexed as to what that is doing there: it is really not a standard textbook result. I seem to recall that this theorem gets used for something later on in the book, though: let's wait and see. (I am almost halfway through my year long course and we have currently covered about the first 13 chapters.) I have some lecture notes for this course I'm teaching -- you're more than welcome to take a look at them. Here ( Wayback Machine ) is the main course page. This handout on differentiation and this handout including the "Monotone Jump Theorem" (on discontinuities of monotone functions) are directly relevant to your question. | {} | {'log_upvote_score': 6, 'links': ['https://math.stackexchange.com/questions/87951', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/9246/']} | jdg_70663 |
stackexchange | llm_judgeable_groundtruth_similarity | 319667 |
Below is a question asked on the forum unix.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
If I type command on my terminal, I don't get "command not found", and the exit code is 0. I assume that this means command actually does something on bash. Also, command -h returns: bash: command: -h: invalid optioncommand: usage: command [-pVv] command [arg ...] What is it used for?
Now provide the response and nothing else.
| From help command : $ help commandcommand: command [-pVv] command [arg ...] Execute a simple command or display information about commands. Runs COMMAND with ARGS suppressing shell function lookup, or display information about the specified COMMANDs. Can be used to invoke commands on disk when a function with the same name exists. Options: -p use a default value for PATH that is guaranteed to find all of the standard utilities -v print a description of COMMAND similar to the `type' builtin -V print a more verbose description of each COMMAND Exit Status: Returns exit status of COMMAND, or failure if COMMAND is not found. As a more general note, rather than just using -h when you don't know what a command does, you should try: type -a command Which would in this case have told you it is a shell builtin. help command is good for shell builtins. For other commands (and also for shell builtins, actually), try man somecommand Also, -h is not necessarily the "help" option. If you don't know what a command does, that may not be a safe assumption to make. Safer is --help . somecommand --help (Common commands where -h is a valid option but does not mean "help" are ls , free , df , du . All of these are informational only, but the assumption that -h will only ever mean "help" is a dangerous assumption.) | {} | {'log_upvote_score': 4, 'links': ['https://unix.stackexchange.com/questions/319667', 'https://unix.stackexchange.com', 'https://unix.stackexchange.com/users/141689/']} | jdg_70664 |
stackexchange | llm_judgeable_groundtruth_similarity | 154724 |
Below is a question asked on the forum stats.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
In the standard maximum likelihood setting (iid sample $Y_{1}, \ldots, Y_{n}$ from some distribution with density $f_{y}(y|\theta_{0}$)) and in case of a correctly specified model the Fisher information is given by $$I(\theta) = -\mathbb{E}_{\theta_{0}}\left[\frac{\partial^{2}}{\theta^{2}}\ln f_{y}(\theta) \right]$$ where the expectation is taken with respect to the true density that generated the data. I have read that the observed Fisher information $$\hat{J}(\theta) = -\frac{\partial^{2}}{\theta^{2}}\ln f_{y}(\theta)$$ is used primary because the integral involved in calculating the (expected) Fisher Information might not be feasible in some cases. What confuses me is that even if the integral is doable, expectation has to be taken with respect to the true model, that is involving the unknown parameter value $\theta_{0}$. If that is the case it appears that without knowing $\theta_{0}$ it is impossible to compute $I$. Is this true?
Now provide the response and nothing else.
| You've got four quanties here: the true parameter $\theta_0$, a consistent estimate $\hat \theta$, the expected information $I(\theta)$ at $\theta$ and the observed information $J(\theta)$ at $\theta$.These quantities are only equivalent asymptotically, but that is typically how they are used. The observed information $$J (\theta_0) = \frac{1}{N} \sum_{i=1}^N \frac{\partial^2}{\partial \theta_0^2} \ln f( y_i|\theta_0)$$converges in probability to the expected information$$I(\theta_0) = E_{\theta_0} \left[ \frac{\partial^2}{\partial \theta_0^2} \ln f( y| \theta_0) \right]$$when $Y$ is an iid sample from $f(\theta_0)$. Here $ E_{\theta_0} (x)$ indicates the expectation w/r/t the distribution indexed by $\theta_0$: $\int x f(x | \theta_0) dx$.This convergence holds because of the law of large numbers, so the assumption that $Y \sim f(\theta_0)$ is crucial here. When you've got an estimate $\hat \theta$ that converges in probability to the true parameter $\theta_0$ (ie, is consistent) then you can substitute it for anywhere you see a $\theta_0$ above, essentially due to the continuous mapping theorem$^*$, and all of the convergences continue to hold. $^*$ Actually, it appears to be a bit subtle . Remark As you surmised, observed information is typically easier to work with because differentiation is easier than integration, and you might have already evaluated it in the course of some numeric optimization. In some circumstances (the Normal distribution) they will be the same. The article "Assessing the Accuracy of the Maximum Likelihood Estimator: Observed Versus ExpectedFisher Information" by Efron and Hinkley (1978) makes an argument in favor of the observed information for finite samples. | {} | {'log_upvote_score': 5, 'links': ['https://stats.stackexchange.com/questions/154724', 'https://stats.stackexchange.com', 'https://stats.stackexchange.com/users/45674/']} | jdg_70665 |
stackexchange | llm_judgeable_groundtruth_similarity | 34378707 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
This is my Activity code, Long time = new GregorianCalendar().getTimeInMillis()+20000;//Setting alarm after 20 secIntent intentAlarm = new Intent("alarm");intentAlarm.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);intentAlarm.putExtra("req_code",10);PendingIntent pendingIntent = PendingIntent.getBroadcast(context,10, intentAlarm, PendingIntent.FLAG_UPDATE_CURRENT);AlarmManager alarmManager = (AlarmManager) getSystemService(Context.ALARM_SERVICE);alarmManager.set(AlarmManager.RTC_WAKEUP, time, pendingIntent); These are all the permissions that I have in my app, <uses-permission android:name="android.permission.VIBRATE" /> <uses-permission android:name="android.permission.INTERNET"/> <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/> <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/> <uses-permission android:name="android.permission.GET_ACCOUNTS"/> <uses-permission android:name="com.myapp.pack.permission.SET_ALARM"/> <uses-permission android:name="android.permission.WAKE_LOCK" /> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> This is my BroadcastReceiver code, @Overridepublic void onReceive(Context context, Intent intent) { SharedPreferences sharedPreferences = context.getSharedPreferences( "mydata", Context.MODE_PRIVATE); SharedPreferences.Editor editor = sharedPreferences.edit(); editor.putBoolean("elligible",true); editor.apply(); } I have registered my BroadcastReceiver in the manifest, <receiver android:name="com.myapp.pack.AlarmReciever" android:enabled="true"> <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED" /> <action android:name="alarm" /> </intent-filter> </receiver> The above code successfully executes the BroadcastReceiver on pre-MarshMallow devices in the background ,but on a MarshMallow device ,the BroadcastReceiver does not get executed. Does anyone know what could be happening here? Thanks.
Now provide the response and nothing else.
| There are a couple of things you can try which, when used in concert, should be able to cut through all of the idle/standby/doze modes (irrespective of OS version). 1. Use a WakefulBroadcastReceiver instead of an ordinary BroadcastReceiver . Make sure you include the WAKE_LOCK permission to use it correctly. 2. Use the setExactAndAllowWhileIdle() method (on API 23 & above) to schedule the Intent for the receiver: if(Build.VERSION.SDK_INT < 23){ if(Build.VERSION.SDK_INT >= 19){ setExact(...); } else{ set(...); }}else{ setExactAndAllowWhileIdle(...);} References: 1. Alarm manager for background services . 2. A flowchart for background work, alarms, and your Android app . | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/34378707', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/4581287/']} | jdg_70666 |
stackexchange | llm_judgeable_groundtruth_similarity | 20980450 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Often, I find that I must instantiate a bunch of objects, but I find it easier to supply the parameters for this instantiation as a human-readable text file, which I manually compose and feed into the program as input. For instance, if the object is a Car then the file might be a bunch of rows, each containing the name, speed and color (the three mandatory constructor parameters) delimited with tabs: My car 65 RedArthur's car 132 PinkOld junk car 23 Rust brown This is easy for me to inspect visually, modify or generate by another program. The program can then load the file, take each row, parse out the relevant parameters, feed them into a Car(string name, int speed, uint color) constructor and create the object. Notice how there is some work that must be done on the input before it is compatible with the constructor: The speed must be converted from string to int with a call to int.Parse . The color must be matched to a RGB value by looking up the English color name (perhaps the program would access Wikipedia to figure out each color's value, or consults a predefined map of name -> RGB somewhere). My question is, from an OOP standpoint, who should do this parsing? The constructor, or the method calling the constructor? With the first option, the advantage is simplicity. The calling function must only do: foreach(var row in input_file) list_of_objects_that_i_am_populating.Add(new Car(row)); And all the ugly parsing can be nicely contained in the constructor, which doesn't have much other code anyhow, so the parsing code can be easily read and modified without being distracted by non-parsing code. The disadvantage is that code reuse goes out the window because now my object is joined at the hip to an input format (worse, because the input format is ad-hoc and manually composed, it is ephemeral and potentially not guaranteed to stay the same). If I reuse this object in another program, where I decide that it is convenient to slightly change the formatting of the input file, the two versions of the object definition are now divergent. I often find myself defining input formats in the comment section of the constructor, which seems a bit code-smelly. Another disadvantage is that I have lost the ability to do batch operations. Recall the earlier example problem of mapping color names to values: What if I was using a web service that takes 1 minute to process every individual request, regardless of whether that request is asking to convert one color name or a million. With a very large input file, I would drastically slow down my application by accessing the service once for each row, instead of submitting one big request for all rows, and then instantiating the objects according to the reply. What is the "correct" way to handle a situation like this? Should I parse input the constructor and treat the problems above as exceptional issues that must be dealt with on a case-by-case basis? Should I let my calling method do the parsing (even though it may already be bloated with much convoluted program logic)?
Now provide the response and nothing else.
| I would create and use factory methods to load via a settings file, or csv. I would NOT put such code in the constructor itself. Factory version 1: public class Car{ ... your existing methods and data ... public static Car CreateFromCsv(string csv ) { .... } public static Car CreateFromFile(string fileName) { ...} } Or use a dedicated Factory: public static class CarFactory{ public static Car CreateFromCsv(string csv ) { .... } public static Car CreateFromFile(string fileName) { ...}} Or a dedicated business logic class: namespace BusinessLogic;public class LoadCars{ public Car ExecuteForCsv(string csv) { ...} public Car ExecuteForFile(string fileName) { ... }} | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/20980450', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1042555/']} | jdg_70667 |
stackexchange | llm_judgeable_groundtruth_similarity | 17250568 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have an array of N elements (representing the N letters of a given alphabet), and each cell of the array holds an integer value, that integer value meaning the number of occurrences in a given text of that letter. Now I want to randomly choose a letter from all of the letters in the alphabet, based on his number of appearances with the given constraints: If the letter has a positive (nonzero) value, then it can be always chosen by the algorithm (with a bigger or smaller probability, of course). If a letter A has a higher value than a letter B, then it has to be more likely to be chosen by the algorithm. Now, taking that into account, I've come up with a simple algorithm that might do the job, but I was just wondering if there was a better thing to do. This seems to be quite fundamental, and I think there might be more clever things to do in order to accomplish this more efficiently. This is the algorithm i thought: Add up all the frequencies in the array. Store it in SUM Choosing up a random value from 0 to SUM. Store it in RAN [While] RAN > 0, Starting from the first, visit each cell in the array (in order), and subtract the value of that cell from RAN The last visited cell is the chosen one So, is there a better thing to do than this? Am I missing something? I'm aware most modern computers can compute this so fast I won't even notice if my algorithm is inefficient, so this is more of a theoretical question rather than a practical one. I prefer an explained algorithm rather than just code for an answer, but If you're more comfortable providing your answer in code, I have no problem with that.
Now provide the response and nothing else.
| The idea: Iterate through all the elements and set the value of each element as the cumulative frequency thus far. Generate a random number between 1 and the sum of all frequencies Do a binary search on the values for this number (finding the first value greater than or equal to the number). Example: Element A B C DFrequency 1 4 3 2Cumulative 1 5 8 10 Generate a random number in the range 1-10 (1+4+3+2 = 10, the same as the last value in the cumulative list), do a binary search, which will return values as follows: Number Element returned1 A2 B3 B4 B5 B6 C7 C8 C9 D10 D | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/17250568', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/2475260/']} | jdg_70668 |
stackexchange | llm_judgeable_groundtruth_similarity | 19057754 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am having issues with a gem and found that someone was able to fix it in this pull request: https://github.com/rheaton/carrierwave-video/pull/13 How can I integrate this change into my app locally since it has been merged yet?
Now provide the response and nothing else.
| Assuming you're using Bundler, you can specify the repository and branch to use for the gem in your Gemfile (it also supports specifying a tag or a reference hash, but a branch should work for your case). In this case, it might look something like: gem 'carrierwave-video', :git => 'git://github.com/elja/carrierwave-video.git', :branch => 'patch-1' or, more concisely: gem 'carrierwave-video', :github => 'elja/carrierwave-video', :branch => 'patch-1' This isn't a great long-term solution, since the branch is unlikely to continue to keep up to date properly, and might disappear, so you should probably switch back to the default as soon as the pull request is resolved. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/19057754', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1720985/']} | jdg_70669 |
stackexchange | llm_judgeable_groundtruth_similarity | 4014053 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am currently pondering the feasability of implementing part of the Android APIs on a desktop JVM and I was wondering whether you had already heard of such a project. If there aren't, and you know good reasons why (beyond "no one has begun that yet"), I would be glad to read them.
Now provide the response and nothing else.
| EDIT: I've now blogged about this in more detail. My original (and I now believe incorrect) thought: generic constraints aren't taken into account during the overload resolution and type inference phases - they're only used to validate the result of the overload resolution. EDIT: Okay, after a lot of going round on this, I think I'm there. Basically my first thought was almost correct. Generic type constraints only act to remove methods from a candidate set in a very limited set of circumstances... in particular, only when the type of a parameter itself is generic; not just a type parameter, but a generic type which uses a generic type parameter. At that point, it's the constraints on the type parameters of the generic type which are validated, not the constraints on the type parameters of the generic method you're calling. For example: // Constraint won't be considered when building the candidate setvoid Foo<T>(T value) where T : struct// The constraint *we express* won't be considered when building the candidate// set, but then constraint on Nullable<T> willvoid Foo<T>(Nullable<T> value) where T : struct So if you try to call Foo<object>(null) the above method won't be part of the candidate set, because Nullable<object> value fails to satisfy the constraints of Nullable<T> . If there are any other applicable methods, the call could still succeed. Now in the case above, the constraints are exactly the same... but they needn't be. For example, consider: class Factory<TItem> where TItem : new()void Foo<T>(Factory<T> factory) where T : struct If you try to call Foo<object>(null) , the method will still be part of the candidate set - because when TItem is object , the constraint expressed in Factory<TItem> still holds, and that's what's checked when building up the candidate set. If this turns out to be the best method, it will then fail validation later, near the end of 7.6.5.1: If the best method is a generic method, the type arguments (supplied or inferred) are checked against the constraints (§4.4.4) declared on the generic method. If any type argument does not satisfy the corresponding constraint(s) on the type parameter, a binding-time error occurs. Eric's blog post contains more detail on this. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/4014053', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/113158/']} | jdg_70670 |
stackexchange | llm_judgeable_groundtruth_similarity | 53844052 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am learning to build apps in Flutter. Now I have come to alert dialogs. I have done them before in Android and iOS , but how do I make an alert in Flutter? Here are some related SO questions: How to style AlertDialog Actions in Flutter adding dropdown menu in alert dialog box in flutter Show alert dialog on app main screen load automatically how to refresh alertdialog in flutter Alert Dialog with Rounded corners in flutter I'd like to make a more general canonical Q&A so my answer is below.
Now provide the response and nothing else.
| One Button showAlertDialog(BuildContext context) { // set up the button Widget okButton = TextButton( child: Text("OK"), onPressed: () { }, ); // set up the AlertDialog AlertDialog alert = AlertDialog( title: Text("My title"), content: Text("This is my message."), actions: [ okButton, ], ); // show the dialog showDialog( context: context, builder: (BuildContext context) { return alert; }, );} Two Buttons showAlertDialog(BuildContext context) { // set up the buttons Widget cancelButton = TextButton( child: Text("Cancel"), onPressed: () {}, ); Widget continueButton = TextButton( child: Text("Continue"), onPressed: () {}, ); // set up the AlertDialog AlertDialog alert = AlertDialog( title: Text("AlertDialog"), content: Text("Would you like to continue learning how to use Flutter alerts?"), actions: [ cancelButton, continueButton, ], ); // show the dialog showDialog( context: context, builder: (BuildContext context) { return alert; }, );} Three Buttons showAlertDialog(BuildContext context) { // set up the buttons Widget remindButton = TextButton( child: Text("Remind me later"), onPressed: () {}, ); Widget cancelButton = TextButton( child: Text("Cancel"), onPressed: () {}, ); Widget launchButton = TextButton( child: Text("Launch missile"), onPressed: () {}, ); // set up the AlertDialog AlertDialog alert = AlertDialog( title: Text("Notice"), content: Text("Launching this missile will destroy the entire universe. Is this what you intended to do?"), actions: [ remindButton, cancelButton, launchButton, ], ); // show the dialog showDialog( context: context, builder: (BuildContext context) { return alert; }, );} Handling button presses The onPressed callback for the buttons in the examples above were empty, but you could add something like this: Widget launchButton = TextButton( child: Text("Launch missile"), onPressed: () { Navigator.of(context).pop(); // dismiss dialog launchMissile(); },); If you make the callback null , then the button will be disabled. onPressed: null, Supplemental code Here is the code for main.dart in case you weren't getting the functions above to run. import 'package:flutter/material.dart';void main() => runApp(MyApp());class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter', home: Scaffold( appBar: AppBar( title: Text('Flutter'), ), body: MyLayout()), ); }}class MyLayout extends StatelessWidget { @override Widget build(BuildContext context) { return Padding( padding: const EdgeInsets.all(8.0), child: ElevatedButton( child: Text('Show alert'), onPressed: () { showAlertDialog(context); }, ), ); }}// replace this function with the examples aboveshowAlertDialog(BuildContext context) { ... } | {} | {'log_upvote_score': 9, 'links': ['https://Stackoverflow.com/questions/53844052', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/3681880/']} | jdg_70671 |
stackexchange | llm_judgeable_groundtruth_similarity | 9263457 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am very, very new to unit testing and am trying to write a test for a pretty simple method: public class myClass : RequireHttpsAttribute{ public override void OnAuthorization(AuthoizationContext filterContext) { var request = filterContext.HttpContext.Request; var header = Convert.ToBoolean(request.Headers["Special-Header-Name"]); if (!(header || request.IsSecureConnection)) { HandleNonHttpsRequest(filterContext); } }} This method, which inherits from the RequireHttpsAttribute , checks if a certain header is present from a page, if it's missing or false, and the page is not secure, then it will call HandleNonHttpsRequest , otherwise it does nothing. We are using Moq and Nunit for testing. I have found some resources to help build a fakeHttpContext with Moq, but honestly I'm not sure how to use it or where to go within my unit tests to ensure that fake HttpContexts are or are not causing the HandleNonHttpsRequest method to call. I really appreciate any guidance with this issue.
Now provide the response and nothing else.
| // arrangevar context = new Mock<HttpContextBase>();var request = new Mock<HttpRequestBase>();var headers = new NameValueCollection{ { "Special-Header-Name", "false" }};request.Setup(x => x.Headers).Returns(headers);request.Setup(x => x.HttpMethod).Returns("GET");request.Setup(x => x.Url).Returns(new Uri("http://www.example.com"));request.Setup(x => x.RawUrl).Returns("/home/index");context.Setup(x => x.Request).Returns(request.Object);var controller = new Mock<ControllerBase>();var actionDescriptor = new Mock<ActionDescriptor>();var controllerContext = new ControllerContext(context.Object, new RouteData(), controller.Object);var filterContext = new AuthorizationContext(controllerContext, actionDescriptor.Object);var sut = new myClass();// actsut.OnAuthorization(filterContext);// assertAssert.IsInstanceOfType(filterContext.Result, typeof(RedirectResult));var redirectResult = (RedirectResult)filterContext.Result;Assert.AreEqual("https://www.example.com/home/index", redirectResult.Url); | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/9263457', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1193187/']} | jdg_70672 |
stackexchange | llm_judgeable_groundtruth_similarity | 2902731 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I came across bitwise operations in C programming, and I realized that XOR operator can be used to swap 2 numbers in their binary bases. For example let $$i=(65)_{10}=(1000001)_{2}, \text{ and } j=(120)_{10}=(1111000)_{2}$$. Let $\oplus$ be the XOR operator, then observe that if I started with any one of them, say $i$ and following the following procedure: 1)replace its value with the $\oplus$ value, yielding $$i=(0111001)_{2},j=(1111000)_{2}$$ 2) replace the other variable($j$) with another $\oplus$ value derived from the new $i$ and old $j$, yielding $$i=(0111001)_{2},j=(1000001)_{2}$$ 3)replace the original variable $i$ with $\oplus$ value again, yielding $$i=(1111000)_{2},j=(1000001)_{2}$$ which shows that we would somehow have their values swapped. I found this way of programming online and I definitely can’t understand how people think of the logic aspect of this. I would think it’s linked to the truth table as follows, which shows by division of cases that the values can be swapped. However, I am still uncertain about the full reasoning why this works, like whether there is any mathematical theorems that I should know that can aid me in my understanding. PS: Sorry if the question is off-topic here, it feels like a programming question, but I feel that I more concerned about the “logic” rather than the programming. I also drew the table myself on MS word since I can't get the latex one to work somehow.
Now provide the response and nothing else.
| In algebraic terms, the XOR operator (or $\oplus$) is nothing other than addition modulo $2$: use $1$ and $0$ for true and false , along with $1 \oplus 1 = 0$. Now, since addition modulo $2$ is associative and commutative , and both elements are their own inverses, we have$$\begin{align}d &= b \oplus c\\&= b \oplus (a \oplus b)\\&= b \oplus (b \oplus a)\\&= (b \oplus b) \oplus a\\&= a.\\\end{align}$$ We can show $e = b$ using similar reasoning. | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/2902731', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/525184/']} | jdg_70673 |
stackexchange | llm_judgeable_groundtruth_similarity | 7908357 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a blog that has a sidebar with a partial view in it that enables users to sign up for my e-mail newsfeed. What I'm trying to do is returning the user to the page they came from after posting some data, and displaying any validation or return messages in the form's partial view. The problem is that my partial view opens in a new window (without the lay-out). How can I fix this so it returns to my blog, with the return data in de sidebar? This is my view: @using Blog.Models.Entities@model Subscriber<header> <h2>Subscribe</h2></header><p>Subscribe to my e-mail newsfeed.</p>@using (Html.BeginForm("Form", "Subscription")){ <div class="editor-label">@Html.LabelFor(subscriber => subscriber.Email)</div> <div class="editor-field ">@Html.EditorFor(subscriber => subscriber.Email)</div> @Html.ValidationMessageFor(subscriber => subscriber.Email) <input type="submit" value="Subscribe" /> <p>@ViewBag.Result</p>} And the relevant pieces of controller that are processing the data: public ActionResult Form(){ return PartialView("_Form");}[HttpPost]public ActionResult Form(Subscriber subscriber){ if (ModelState.IsValid) { Subscriber foundSubscriber = _repository.Subscribers.Where(s => s.Email.Equals(subscriber.Email)).FirstOrDefault(); if (foundSubscriber != null) { ModelState.AddModelError("Email", "This e-mail address has already been added."); return PartialView("_Form", subscriber); } _repository.SaveSubscriber(subscriber); ViewBag.Result = "Succesfully subscribed to the newsletter."; return PartialView("_Form"); } ModelState.AddModelError("Email", "Please provide a valid e-mail address."); return PartialView("_Form", subscriber);}
Now provide the response and nothing else.
| The type (s -> t) -> [s] -> [t] can be read in two ways. One way is to treat it as a function of two arguments, the first a function of type s -> t and the second a list of type [s] . The return value is of type [t] . The other way is to understand that function arrows are right-associative, so the type is equivalent to (s -> t) -> ([s] -> [t]) . Under this interpretation, map is a function that takes a function from element to element s -> t and turns it into a function from list to list [s] -> [t] . Similarly, when using the function, you can think of map foo xs as applying the function map to two arguments foo and xs . Or, since function application is left -associative, you can think of it as (map foo) xs , applying map to the single argument foo to get back a new function which you then apply to xs . Since Haskell functions are curried , these are just two ways of looking at the exact same thing. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/7908357', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/854791/']} | jdg_70674 |
stackexchange | llm_judgeable_groundtruth_similarity | 52914568 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm trying to start a service from a fragment but my code doesn't seem to run properly or I think there is something wrong with how I deal with contexts. It runs ok when I start my service from inside an activity but it doesn't work inside a fragment. This is my fragment class: class OnAirFragment : BaseFragment() { private var play = "Play" private var playValue = false private lateinit var updatePlaybackUI: BroadcastReceiver private var playWhenReady = "Play State" private var playbackState = "Playback State" private var isClicked = false override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? { // Inflate the layout for this fragment val view = inflater.inflate(R.layout.fragment_on_air, container, false) view.start.setOnClickListener { Log.d("TEST", "TAP") if (!isClicked) { Log.d("TEST2", "TAP2") start.setBackgroundResource(R.drawable.ic_pause_empty) val intent = Intent(context, PlaybackService::class.java) intent.putExtra(play, playValue) Util.startForegroundService(context, intent) var intentToService = Intent("activity.to.service.transfer") intentToService.putExtra("x", true) context!!.sendBroadcast(intentToService) val filter = IntentFilter() filter.addAction("service.to.activity.transfer") updatePlaybackUI = object : BroadcastReceiver() { override fun onReceive(context: Context, intent: Intent?) { // UI update here var playPauseState = intent!!.getBooleanExtra(playWhenReady, true) var stopState = intent.getIntExtra(playbackState, Int.MAX_VALUE) if (!playPauseState || stopState == 1) { start.setBackgroundResource(R.drawable.ic_play_empty) isClicked = false } else { start.setBackgroundResource(R.drawable.ic_pause_empty) } } } context!!.registerReceiver(updatePlaybackUI, filter) isClicked = !isClicked } else { Log.d("TEST3", "TAP3") playValue = false start.setBackgroundResource(R.drawable.ic_play_empty) val intent = Intent(context, PlaybackService::class.java) intent.putExtra(play, playValue) context!!.stopService(intent) isClicked = !isClicked } } return view }} And this is my service class: class PlaybackService : Service() { private var player: SimpleExoPlayer? = null private var playerNotificationManager: PlayerNotificationManager? = null private var mediaSession: MediaSessionCompat? = null private lateinit var receiver: BroadcastReceiver private var playWhenReady = "Play State" private var playbackState = "Playback State" override fun onCreate() { super.onCreate() val context = this player = ExoPlayerFactory.newSimpleInstance(context, DefaultTrackSelector()) val dataSourceFactory = DefaultDataSourceFactory( context, Util.getUserAgent(context, "Exo")) val mediaUri = Uri.parse("http://www.radioideal.net:8026/;") val mediaSource = ExtractorMediaSource.Factory(dataSourceFactory) .createMediaSource(mediaUri) player!!.prepare(mediaSource) player!!.playWhenReady = true val filter = IntentFilter() filter.addAction("activity.to.service.transfer") receiver = object : BroadcastReceiver() { override fun onReceive(context: Context, intent: Intent?) { var play = intent!!.getBooleanExtra("x", true) player!!.playWhenReady = play } } registerReceiver(receiver, filter) player?.addListener(eventListener) playerNotificationManager = PlayerNotificationManager.createWithNotificationChannel( context, "BREAKFAST RADIO", R.string.exo_download_notification_channel_name, 1000, object : PlayerNotificationManager.MediaDescriptionAdapter { override fun getCurrentContentTitle(player: Player): String { return "BR Live" } @Nullable override fun createCurrentContentIntent(player: Player): PendingIntent? { return null } @Nullable override fun getCurrentContentText(player: Player): String? { return "BR Live" } @Nullable override fun getCurrentLargeIcon(player: Player, callback: PlayerNotificationManager.BitmapCallback): Bitmap? { return BitmapFactory.decodeResource(context.resources, R.drawable.exo_controls_play) } } ) playerNotificationManager!!.setNotificationListener(object : PlayerNotificationManager.NotificationListener { override fun onNotificationStarted(notificationId: Int, notification: Notification) { startForeground(notificationId, notification) } override fun onNotificationCancelled(notificationId: Int) { stopSelf() } }) playerNotificationManager!!.setPlayer(player) playerNotificationManager?.setFastForwardIncrementMs(0) playerNotificationManager?.setRewindIncrementMs(0) playerNotificationManager?.setUseNavigationActions(false) val playbackStateBuilder = PlaybackStateCompat.Builder() playbackStateBuilder.setActions(PlaybackStateCompat.ACTION_PLAY or PlaybackStateCompat.ACTION_PAUSE) mediaSession = MediaSessionCompat(context, "BREAKFAST") mediaSession!!.isActive = true mediaSession?.setPlaybackState(playbackStateBuilder.build()) playerNotificationManager!!.setMediaSessionToken(mediaSession!!.sessionToken) } override fun onDestroy() { mediaSession!!.release() playerNotificationManager!!.setPlayer(null) player!!.release() player = null super.onDestroy() } @Nullable override fun onBind(intent: Intent): IBinder? { return null } override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int { return Service.START_STICKY } private var eventListener: Player.EventListener = object : Player.EventListener { override fun onPlaybackParametersChanged(playbackParameters: PlaybackParameters?) { var i = 0 } override fun onSeekProcessed() { var i = 0 } override fun onTracksChanged(trackGroups: TrackGroupArray?, trackSelections: TrackSelectionArray?) { var i = 0 } override fun onPlayerError(error: ExoPlaybackException?) { var i = 0 } override fun onLoadingChanged(isLoading: Boolean) { var i = 0 } override fun onPositionDiscontinuity(reason: Int) { var i = 0 } override fun onRepeatModeChanged(repeatMode: Int) { var i = 0 } override fun onShuffleModeEnabledChanged(shuffleModeEnabled: Boolean) { var i = 0 } override fun onTimelineChanged(timeline: Timeline?, manifest: Any?, reason: Int) { var i = 0 } override fun onPlayerStateChanged(playWhenReady: Boolean, playbackState: Int) { sendPlaybackState(playWhenReady, playbackState) } } private fun sendPlaybackState(playWhenReadyValue: Boolean, playbackStateValue: Int) { var intent = Intent("service.to.activity.transfer") intent.putExtra(playWhenReady, playWhenReadyValue) intent.putExtra(playbackState, playbackStateValue) sendBroadcast(intent) }} and I'm not sure my broadcast receivers work either.
Now provide the response and nothing else.
| This is because when you test your lambda with a packet, say { "var1": "2017-04-17T18:48:03.608Z", "var2": "0.45", "var3": "0.5"} Then that packet is passed as the event to the handler. However, you are doing JSON.parse(event.body) , but for the above packet, event.body is undefined (which has token u at position 0). You should change your test packet to: { "body": "{\"var1\":\"2017-04-17T18:48:03.608Z\",\"var2\":\"0.45\",\"var3\":\"0.5\"}"} Note that the body is a stringified JSON, because API Gateway Lambdas expect event body in a stringified format. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/52914568', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/9719937/']} | jdg_70675 |
stackexchange | llm_judgeable_groundtruth_similarity | 190227 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Assume my objects are in perfect working order (i.e. TDD makes me think they work). I have a list that I create like this (except indented properly): var result = from v in vendors from p in v.Products orderby p.Name select p; This works - I get all products from all vendors. Now I have a list of conditions, built up at runtime by the user. Let's apply them: foreach (Attribute a in requiredAttributes){ result = result.Where(p => p.Attributes.Contains(a));} This may be primitive, but I thought it'd work. However, after this foreach loop is finished, when you enumerate "result" it will contain all products that has the LAST Attribute of the requiredAttributes collection in it's Attributes property (also a collection). To me, this smells like "a" is overwritten somewhere with each trip trough the loop, and only the last one applies. Short of somehow writing an extension method to IEnumerable called ContainsAll(IEnumerable) or something to that effect, how can I achieve what I want, which is basically a logical AND, giving me only those products that has ALL the required attributes?
Now provide the response and nothing else.
| (Edited for clarity.) The problem is the foreach loop, and the fact that the "a" variable is being captured and then changed each time. Here's a modification which will work, by effectively introducing a "new" variable for each iteration of the loop, and capturing that new variable. foreach (Attribute a in requiredAttributes){ Attribute copy = a; result = result.Where(p => p.Attributes.Contains(copy));} Omer's solution is a cleaner one if you can use it, but this may help if your real code is actually more complicated :) EDIT: There's more about the issue in this closures article - scroll down to "Comparing capture strategies: complexity vs power". | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/190227', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/2122/']} | jdg_70676 |
stackexchange | llm_judgeable_groundtruth_similarity | 154373 |
Below is a question asked on the forum physics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I was always taught that $\frac d {dx} (\ln x) = \frac 1 x$. No derivative had as a result any $dx$ words.In a physics book I encountered something like this (error discussion) [there might be a little difference, as I don't have the book right now]: We have $\ln a + \ln b = \ln c$. So after deriving both sides we get $\frac {da} a + \frac {db}b = \frac {dc}c $ Why is this small difference $da, db, dc$ put in there? Why isn't it $\frac 1a + \frac 1b = \frac 1c $ ? And what are we differentiating in reference to? $x$, $a$ or what? Another example [this is exactly like this]: We have $[(\frac 1 {S_1}+\frac 1 {S_2})\rho g V + p_0]V = nRT$. Let's treat V as a function of T and differentiate both sides wrt T. Then we have $2(\frac 1 {S_1}+\frac 1 {S_2})\rho g V \frac {dV} {dT} + p_0 \frac {dV} {dT} = nR$ Once again, why are we adding this difference quotient $\frac {dV} {dT}$? Is this as the derivative of the internal function?
Now provide the response and nothing else.
| Regarding your first question, note that $$\frac{d}{dx}\ln c = \frac{1}{c}\frac{dc}{dx}$$ Thus $$\frac{1}{a}\frac{da}{dx} + \frac{1}{b}\frac{db}{dx} = \frac{1}{c}\frac{dc}{dx}$$ Then, as physicists often do, 'cancel' the $dx$ on both sides to yield $$\frac{da}{a} + \frac{db}{b} = \frac{dc}{c}$$ Regarding your second question, it is stated that $V = V(t)$ thus it is elementary that $$\frac{d}{dt}KV(t) = K\frac{dV}{dt}$$ | {} | {'log_upvote_score': 5, 'links': ['https://physics.stackexchange.com/questions/154373', 'https://physics.stackexchange.com', 'https://physics.stackexchange.com/users/66152/']} | jdg_70677 |
stackexchange | llm_judgeable_groundtruth_similarity | 3615476 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I successfully complied this code: #include <stdio.h>#include <math.h>int q;int main(){ srand( time(NULL) ); int n=3; q=ceil(sqrt(n)); printf("%d\n %d\n", n,q); if(n == 2) printf("%d\n is prime", n); else if(n % 2 == 0.0 || n < 2) printf("%d\n is not prime", n); else { int x; for(x = 0; x < q; x++){ if(n % x == 0) { printf("%d\n is not prime", n); return; } else printf("%d\n is prime", n); } }} But when I run my code I get the following error: Floating point exception What does this error mean and how can I fix it?
Now provide the response and nothing else.
| It's caused by n % x , when x is 0. You should have x start at 2 instead. You should not use floating point here at all, since you only need integer operations. General notes: Try to format your code better. Focus on using a consistent style. E.g. you have one else that starts immediately after a if brace (not even a space), and another with a newline in between. Don't use globals unless necessary. There is no reason for q to be global. Don't return without a value in a non-void (int) function. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/3615476', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/436652/']} | jdg_70678 |
stackexchange | llm_judgeable_groundtruth_similarity | 61623 |
Below is a question asked on the forum physics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
It is written in my quantum physics book that the K shell contains only 2 electrons due to the Pauli principle. I know that if $n = 1, l = 0, m = 0$, then the Hilbert space associated to the spin is of dimension $2$. I also know that Pauli principle says that if we have a vector $\lvert\psi\rangle$ which represents the state of N electrons, then $\lvert\psi\rangle$ must be antisymmetric by transposition. But how can we conclude please ?
Now provide the response and nothing else.
| Suppose you had three electrons, with individual wavefunctions $\lvert \psi_1 \rangle$, $\lvert \psi_2 \rangle$, and $\lvert \psi_3 \rangle$. Let them all have the same $\vec{x}$, $l$, and $m$, so they can only differ in intrinsic spin. Since spin is a two-dimensional Hilbert space, as you noted, then three vectors must be linearly dependent. That is, there exist complex numbers $\alpha$ and $\beta$ such that$$ \lvert \psi_3 \rangle = \alpha \lvert \psi_1 \rangle + \beta \lvert \psi_2 \rangle. $$ Now the state of all three electrons is given by the tensor product$$ \lvert 1,2,3 \rangle \equiv \lvert \psi_1 \rangle \otimes \lvert \psi_2 \rangle \otimes \lvert \psi_3 \rangle. $$The tensor product respects the structure of the underlying vector spaces, which is a fancy way of saying we can write$$ \lvert 1,2,3 \rangle = \alpha \lvert 1,2,1 \rangle + \beta \lvert 1,2,2 \rangle. $$But $\lvert 1,2,1 \rangle$, as a product state of identical fermions, is antisymmetric under interchange, in particular under interchance of the $\lvert \psi_1 \rangle$ components:$$ \lvert 1,2,1 \rangle = - \lvert 1,2,1 \rangle. $$Thus $\lvert 1,2,1 \rangle \equiv 0$. Similarly, $\lvert 1,2,2 \rangle$ vanishes. We have just shown that our 3-electron wavefunction is a linear combination of $0$-vectors, and so it too vanishes. This argument easily generalizes to more than three electrons by appending the combined wavefunction of all the others to the end of our state and just carrying it through the computations; that is, just do the same thing splitting up $\lvert \psi_3 \rangle$, but apply it to$$ \lvert 1,2,3 \rangle \otimes \lvert 4,\ldots,n \rangle. $$ | {} | {'log_upvote_score': 4, 'links': ['https://physics.stackexchange.com/questions/61623', 'https://physics.stackexchange.com', 'https://physics.stackexchange.com/users/22952/']} | jdg_70679 |
stackexchange | llm_judgeable_groundtruth_similarity | 2497200 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
In Javascript, is there a technique to listen for changes to the title element?
Now provide the response and nothing else.
| 5 years later we finally have a better solution. Use MutationObserver ! In short: new MutationObserver(function(mutations) { console.log(mutations[0].target.nodeValue);}).observe( document.querySelector('title'), { subtree: true, characterData: true, childList: true }); With comments: // select the target nodevar target = document.querySelector('title');// create an observer instancevar observer = new MutationObserver(function(mutations) { // We need only first event and only new value of the title console.log(mutations[0].target.nodeValue);});// configuration of the observer:var config = { subtree: true, characterData: true, childList: true };// pass in the target node, as well as the observer optionsobserver.observe(target, config); Also Mutation Observer has awesome browser support : | {} | {'log_upvote_score': 7, 'links': ['https://Stackoverflow.com/questions/2497200', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/62255/']} | jdg_70680 |
stackexchange | llm_judgeable_groundtruth_similarity | 23186 |
Below is a question asked on the forum unix.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
How to join, to tsv files, examples: a.tsv c 7 r zd 6 s wf 1 f fb 8 p ya 9 q x b.tsv a q ac r cccb p bb0 0 0d s dddd Here I'd like to "join" them by columns, where a$1,a$3==b$1,b$2 and display rest (a$2,a$4,b$3) : 6 w dddd9 x a8 y bb7 z ccc Question is: how would you do this in gawk ? Order of rows does not metter (in output. In input, order of rows is not defined and can be different in a.tsv and b.tsv - like rows in relational db, they have no order). Uniqueness note : Originally, I assumed "uniqueness of key={a$1,a$3} . As glenn jackman noticed - it can not be assumed from original problem statement, as it allows not unique rows according to any key - thanks glenn .
Now provide the response and nothing else.
| It appears the join command can only join on one field [ 1 , 2 ], so: awk ' BEGIN {FS=OFS="\t"} NR==FNR {a[$1 FS $3] = $2 FS $4; next} $1 FS $2 in a {print a[$1 FS $2], $3}' a.tsv b.tsv Update due to comment: since the given key is not unique, here's a technique to build up multiple entries from "a.tsv" awk ' BEGIN {FS=OFS="\t"} NR==FNR { key = $1 FS $3 if (key in a) a[key] = a[key] "\n" $2 FS $4 else a[key] = $2 FS $4 next } $1 FS $2 in a { split(a[$1 FS $2], ary, /\n/) for (idx in ary) print ary[idx], $3 }' a.tsv b.tsv | {} | {'log_upvote_score': 4, 'links': ['https://unix.stackexchange.com/questions/23186', 'https://unix.stackexchange.com', 'https://unix.stackexchange.com/users/9689/']} | jdg_70681 |
stackexchange | llm_judgeable_groundtruth_similarity | 44694 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
If $a+b+c \neq 0 $ where $a,b$ and $c$ are three non-zero distinct integers, then find the value of: $$\frac{ab+ca}{a^2+ab+ca} + \frac{ab+cb}{b^2+ab+bc} + \frac{ac+cb}{c^2+ac+bc}$$ What confusing me here, is the not so obvious hint which is given with the problem,which says that that form could be written as: $$3- \frac{a^2}{a^2+ab+ca} - \frac{b^2}{b^2+ab+bc} - \frac{c^2}{c^2+ac+bc}$$ But how is this possible?
Now provide the response and nothing else.
| All you need to do is "simplify" the fractions, for example by dividing "top" and "bottom" of the first one by $a$, of the second by $b$, of the third by $c$. We get $$\frac{b+c}{a+b+c}+\frac{a+c}{a+b+c}+\frac{a+b}{a+b+c}$$ We have a common denominator $a+b+c$. The numerators add up to $2(a+b+c)$. Cancel. We get $2$. Comment : If you find this not obvious, let's look at the first term, that is, at$$\frac{ab+ca}{a^2+ab+ca}$$The "top" is $a(b+c)$. The "bottom" is $a(a+b+c)$. So the fraction is$$\frac{a(b+c)}{a(a+b+c)}$$Divide top and bottom by $a$, or equivalently, "cancel" the $a$'s. We are using the "algebra" version of the familiar fact that$$\frac{2\cdot 3}{2 \cdot 5}=\frac{3}{5}$$ Additional comment The hint is strange. True, we can rewrite the expression as $$\left(1-\frac{a^2}{a^2+ab+ca}\right) +\left(1-\frac{b^2}{b^2+ab+bc}\right)+\left(1-\frac{c^2}{c^2+bc+ca}\right)$$which is equivalent to what was given. And then we could divide top and bottom by $a$ in the first fraction, by $b$ in the second, by $c$ in the third, and end up with$$3-\frac{a+b+c}{a+b+c}$$But it sure seems like a lot of work when we can cancel immediately! You are sure that you quoted the problem correctly? | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/44694', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/2109/']} | jdg_70682 |
stackexchange | llm_judgeable_groundtruth_similarity | 5527100 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Nothing I've found has been able to help me solve this one specific case. I recently switched from a plain old java web app project (which was working) to a maven web project. I get the following runtime exception: java.util.MissingResourceException: Can't find bundle for base name com.myapp.config, locale en I am using Netbeans to create a JSF 2.0, Spring, and Hibernate web app. I have the following directory structure: src\main\java\com\myapp Contains config.properties src\main\resources Empty target\myapp\WEB-INF\classes\com\myapp Contains compiled class files without config.properties src\main\java\com\myapp Contains config.properties Inspection of the WAR file in the target folder does not show any sign of the properties file so it's as if the Maven build plug-in is not copying over properties files. I know there is a tag you can place inside the pom but it didn't work for me. The link below mentions that the resources folder (empty for me) has its contents included during the build but if that is the case, how do you do it from Netbeans? I just want the properties file to be packaged with my war so it is accessible when it is deployed to the server. http://maven.apache.org/plugins/maven-war-plugin/examples/adding-filtering-webresources.html pom.xml: <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.myapp</groupId><artifactId>myapp</artifactId><packaging>war</packaging><version>1.0-SNAPSHOT</version><name>myapp</name><url>http://maven.apache.org</url><repositories> <repository> <id>java.net</id> <name>Repository hosting the Java EE 6 artifacts</name> <url>http://download.java.net/maven/2</url> </repository></repositories><dependencies> <dependency> <groupId>javax.faces</groupId> <artifactId>jsf-api</artifactId> <version>2.1</version> <scope>provided</scope> </dependency> <dependency> <groupId>javax</groupId> <artifactId>javaee-web-api</artifactId> <version>6.0</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-hibernate3</artifactId> <version>2.0.8</version> </dependency> <dependency> <groupId>com.amazonaws</groupId> <artifactId>aws-java-sdk</artifactId> <version>1.1.8</version> </dependency> <dependency> <groupId>net.authorize</groupId> <artifactId>java-anet-sdk</artifactId> <version>1.4.2</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.15</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.2</version> <scope>test</scope> </dependency></dependencies><build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>2.3.2</version> <configuration> <source>1.6</source> <target>1.6</target> </configuration> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-war-plugin</artifactId> <version>2.1.1</version> <configuration> <failOnMissingWebXml>false</failOnMissingWebXml> </configuration> </plugin> </plugins> <finalName>${artifactId}</finalName></build><profiles> <profile> <id>endorsed</id> <activation> <property> <name>sun.boot.class.path</name> </property> </activation> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <!-- javaee6 contains upgrades of APIs contained within the JDK itself. As such these need to be placed on the bootclasspath, rather than classpath of the compiler. If you don't make use of these new updated API, you can delete the profile. On non-SUN jdk, you will need to create a similar profile for your jdk, with the similar property as sun.boot.class.path in Sun's JDK.--> <compilerArguments> <bootclasspath>${settings.localRepository}/javax/javaee-endorsed-api/6.0/javaee-endorsed-api-6.0.jar${path.separator}${sun.boot.class.path}</bootclasspath> </compilerArguments> </configuration> <dependencies> <dependency> <groupId>javax</groupId> <artifactId>javaee-endorsed-api</artifactId> <version>6.0</version> </dependency> </dependencies> </plugin> </plugins> </build> </profile></profiles><properties> <netbeans.hint.deploy.server>gfv3ee6</netbeans.hint.deploy.server></properties>
Now provide the response and nothing else.
| What is your project's build path configured to be in Netbeans? You might try changing it to src/main/webapp/WEB-INF/classes . This way class files compiled from your src/main/java folder and any resources you have under src/main/resources should get included in the generated WAR. You would then be able to access your config.properties file if you place it under the src/main/resources folder. You might also review any includes sections in your pom.xml and ensure you're not accidentally excluding something (if you explicitly include some things, you're likely implicitly excluding everything else). | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/5527100', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/689437/']} | jdg_70683 |
stackexchange | llm_judgeable_groundtruth_similarity | 35091 |
Below is a question asked on the forum electronics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I currently make a system consisting of a plastic enclosure which contains an MCU talking to 7 ADCs using 2MHz SPI over wires about 5cm long. The problem is that I'm concerned about EMI. Everything I have read suggests that any kind of digital signal that's not safely on a PCB in a grounded metal chassis will radiate too much to pass EMI testing. I guess this would include I2C as well. Is this likely to fail EMI testing? What can I do about this? I am looking for any kind of answers, including "Use a different bus / ADC", but not including answers that involve mechanical changes like: "Put all the ADCs on the same PCB" or "Put the whole thing in a metal box". I am especially interested in Low-EMI alternatives to SPI including differential buses. Here is some relevant information about the application. Please let me know if you need to know more things: 6 wires go to each ADC board (Power, GND, CS, CLK, MOSI, MISO). ADCs are currently MCP3208 (Microchip 8-channel, 12-bit) I am working in a desperately space constrained application, so adding shielding to the wires isn't really an option. It would be nice to use some kind of differential bus (one or two pairs only), but the only ADCs with differential communication seem to be multi-MSPS LVDS types. CAN is probably too slow, and also kind of bulky for such a space constrained application. Sample rate: I need to sample every channel at 1kHz. Added: Just to give an idea of the space constraints: Here you can see one of the ADC PCBs. This one actually has an MCP3202 instead of an MCP3208, but it's compatible(ish). It's in a TSSOP 8 package. The PCB is 11mm x 13mm. The black cable is 2mm diameter. As you can see, there isn't even space for a connector and the wires are soldered directly to the PCB, then potted. The lack of connector is due to surrounding space constraints rather than PCB space constraints.
Now provide the response and nothing else.
| 2 MHz SPI over 5 cm cables is not huge. I do 30 MHz SPI over 10 cm cables a lot, passing FCC Class B and the CE equivalent. The key is to make sure that you have a good cable (controlling as best you can for loop area), and properly terminating your signals. You control for loop area by putting the power/GND signals somewhere in the middle of the cable: Both middle of the connector, but in the middle of the bundle of wires as well. Normally you'd have a power or GND per signal, but since that is rarely a practical solution you have to do the best with what you have. Also, make sure to put one or two decoupling caps on the PCBs at both ends of the cable. Properly terminating the signals is going to be a little tricky since you don't have a controlled impedance on your cable. What I would do is to put an RC filter on the PCB at both ends of the cable. The RC filter would have the C on the cable side and the R on the chip side. At the signal driver, I would start with an R of about 75 ohms and a C of about 1 nF. At the receiver, the R would be about 10 ohms and C still 1 nF. Once you have the prototypes built then you should try different values. Essentially you want higher values for R and C, but not so high that the thing stops working or the signal levels are too attenuated. The edges of your signals should look very rounded off, but there should be no ringing and the clocks should be nice while in the signal transition band (usually 0.8 to 2.0 volts). A cap value of at least 3 nF is ideal for ESD protection, but that might not be an issue in your application. | {} | {'log_upvote_score': 5, 'links': ['https://electronics.stackexchange.com/questions/35091', 'https://electronics.stackexchange.com', 'https://electronics.stackexchange.com/users/1024/']} | jdg_70684 |
stackexchange | llm_judgeable_groundtruth_similarity | 13912597 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Adding simple e-mail validation to my code, I created the following function: def isValid(email: String): Boolean = if("""(?=[^\s]+)(?=(\w+)@([\w\.]+))""".r.findFirstIn(email) == None)false else true This will pass emails like [email protected] and fail mails like bobtestmymail.com , but mails with space characters slip through, like bob @testmymail will also return true. I'm probably being silly here...
Now provide the response and nothing else.
| My function is inspired from the one that the Play Framework uses (see PlayFramework ) and uses the regexp presented here: W3C recommendation . Hope it helps. All tests suggested in the other questions are passed. private val emailRegex = """^[a-zA-Z0-9\.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$""".rdef check(e: String): Boolean = e match{ case null => false case e if e.trim.isEmpty => false case e if emailRegex.findFirstMatchIn(e).isDefined => true case _ => false} | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/13912597', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/828757/']} | jdg_70685 |
stackexchange | llm_judgeable_groundtruth_similarity | 5962048 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
When installing JDK in my machines (Windows 7), I do the following. install latest 1.7 JDK with the Oracle installer (just the JDK, no JRE ) copy the install folder, to the place I really want, remove samples, etc. uninstall Java set %JAVA_HOME%, add %JAVA_HOME%\bin to %Path% Then I synchronise that folder in all my machines so I keep it updated (with unlimited cryptography stuff, jssecacerts , java.policy , endorsed libraries, etc). BUT this has one big caveat, when Chrome needs to use load a page that uses Java, it thinks Java is not installed and wants to install it. I don't want to install it as it would mess with my 'hand-installed' JDK. So is there a way to configure Chrome so it uses the JDK in my disk?I have both JDK 32-bit and JDK 64-bit, so that is not a problem (I guess I would need to use the 32-bit one with Chrome). I found a question in the Chrome project, How do I have the Chrome Java plugin reference an existing JDK without reinstalling Java? , but no replies so far... UPDATE: for Ubuntu, see Kalyan's answer UPDATE: I still continue to use this approach successfully, last time with 1.7.0_21 on win7 UPDATE for 1.7.45: the path in the windows registry now is [HKEY_LOCAL_MACHINE\SOFTWARE\MozillaPlugins]
Now provide the response and nothing else.
| Apparently, Chrome addresses a key in Windows registry when it looks for a Java Environment. Since the plugin installs the JRE, this key is set to a JRE path and therefore needs to be edited if you want Chrome to work with the JDK. Run the plugin installer anyways. Start -> Run ( Winkey+R ) and then type in regedit to edit the registry. Find HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins\@java.com/JavaPlugin . Export it as a reg file to say, your desktop (right-click and select Export ). Uninstall the JRE (Control Panel -> Add or Remove Programs). This should delete the key above, explaining the need to export it in the first place. Open the reg file exported to your desktop with a text editor (such as Notepad++). Edit "Path" so that it matches the corresponding dll inside your JDK installation: REGEDIT 4[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MozillaPlugins\@java.com/JavaPlugin]"Description"="Oracle® Next Generation Java™ Plug-In""GeckoVersion"="1.9""Path"="C:\Program Files (x86)\Java\jdk1.6.0_29\jre\bin\new_plugin\npjp2.dll""ProductName"="Oracle® Java™ Plug-In""Vendor"="Oracle Corp.""Version"="160_29" Save file. Double click modified reg file to add keys to your registry. The REGEDIT 4 prefix at the top of the file might only be required for Windows 7 64-bit. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/5962048', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/101762/']} | jdg_70686 |
stackexchange | llm_judgeable_groundtruth_similarity | 110658 |
Below is a question asked on the forum softwareengineering.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Once in a while C++ code will not work when compiled with some level of optimization. It may be compiler doing optimization that breaks the code or it may be code containing undefined behavior which allows the compiler to do whatever it feels. Suppose I have some piece of code that breaks when compiled with higher optimizations level only. How do i know if it's the code or the compiler and what do I do if it's the compiler?
Now provide the response and nothing else.
| I would say it is a safe bet that, in the vast majority of the cases, it is your code, not the compiler, that is broken. And even in the extraordinary case when it is the compiler, you are probably using some obscure language feature in an unusual way, for which the specific compiler is not prepared; in other words, you could most likely change your code to be more idiomatic and avoid the weak spot of the compiler. At any rate, if you can prove that you found a compiler bug (based on the language spec), report it the compiler developers, so that they may get it fixed some time. | {} | {'log_upvote_score': 4, 'links': ['https://softwareengineering.stackexchange.com/questions/110658', 'https://softwareengineering.stackexchange.com', 'https://softwareengineering.stackexchange.com/users/587/']} | jdg_70687 |
stackexchange | llm_judgeable_groundtruth_similarity | 32994464 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm trying to establish SSL/TLS connection to test server with self-signed certificate . Communication through unsecure channel worked without issues. Here is my sample code, which I've written based on this solutions: Allowing Untrusted SSL Certificates with HttpClient C# Ignore certificate errors? .NET client connecting to ssl Web API ServicePointManager.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;var c = new HttpClient();var r = c.GetAsync("https://10.3.0.1:8443/rest/v1").Result;if (r.IsSuccessStatusCode){ Log.AddMessage(r.Content.Get<string>());}else{ Log.AddMessage(string.Format("{0} ({1})", (int)r.StatusCode, r.ReasonPhrase));} also tried this: var handler = new WebRequestHandler();handler.ServerCertificateValidationCallback = delegate { return true; };var c = new HttpClient(handler);... and this ServicePointManager.ServerCertificateValidationCallback = delegate { return true; }; but each time I've got an exception: InnerException: System.Net.Http.HttpRequestException _HResult=-2146233088 _message=An error occurred while sending the request. HResult=-2146233088 IsTransient=false Message=An error occurred while sending the request. InnerException: System.Net.WebException _HResult=-2146233079 _message=The request was aborted: Could not create SSL/TLS secure channel. HResult=-2146233079 IsTransient=false Message=The request was aborted: Could not create SSL/TLS secure channel. Source=System StackTrace: at System.Net.HttpWebRequest.EndGetResponse(IAsyncResult asyncResult) at System.Net.Http.HttpClientHandler.GetResponseCallback(IAsyncResult ar) InnerException: What do I do wrong? Why I can't connect to this server (which has invalid-self-signed certificate)
Now provide the response and nothing else.
| You are doing it right with ServerCertificateValidationCallback. This is not the problem you are facing. The problem you are facing is most likely the version of SSL/TLS protocol. For example, if your server offers only SSLv3 and TLSv10 and your client needs TLSv12 then you will receive this error message. What you need to do is to make sure that both client and server have a common protocol version supported. When I need a client that is able to connect to as many servers as possible (rather than to be as secure as possible) I use this (together with setting the validation callback): ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12; | {} | {'log_upvote_score': 9, 'links': ['https://Stackoverflow.com/questions/32994464', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/2588795/']} | jdg_70688 |
stackexchange | llm_judgeable_groundtruth_similarity | 360157 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Is Zariski topology on any irreducible affine curve is same as the cofinite topology.Try: I proved the satement for irreducible affine plane curve.
Now provide the response and nothing else.
| 1) No, despite a widespread misconception, the Zariski topology for any curve seen as a scheme never coincides with the cofinite topology. This is because the curve has a generic point if it is irreducible and several generic points if it is reducible and these points are not closed, so that the Zariski topology cannot be the cofinite topology. (In a cofinite topology all points are closed.) 2) However in elementary algebraic geometry over an algebraically closed field $k$ one may consider only the closed points of the curve, which in the affine pieces correspond to maximal ideals of the relevant $k-$algebra. This is, for example, Fulton's point of view in his celebrated (now freely available online) book Algebraic Curves . In that context it is indeed true that the Zariski topology of the curve coincides with the cofinite topology. | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/360157', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/71960/']} | jdg_70689 |
stackexchange | llm_judgeable_groundtruth_similarity | 11233789 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a subclass of the CoreDataTableViewController (subclass of UITAbleViewController dome by the people on Stanford done to link CoreData and TableViews). On this Class, I want to perform a fecth, sorting by an attribute called "definition" and the code which executes it is the following: - (void)setupFetchedResultsController{ NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:self.entity]; request.propertiesToFetch=[NSArray arrayWithObject:@"definition"]; request.returnsDistinctResults=YES; NSPredicate *predicate1 = [NSPredicate predicateWithFormat:@"%K != nil", @"definition"]; NSPredicate *predicate2 = [NSPredicate predicateWithFormat:@"%K != ''", @"definition"]; NSPredicate *predicate3= [NSPredicate predicateWithFormat:@"%K contains[cd] %@", @"definition", self.seachBar.text]; NSArray *prepredicateArray; if ([self.seachBar.text length]) { prepredicateArray = [NSArray arrayWithObjects:predicate1, predicate2, predicate3,nil]; }else { prepredicateArray = [NSArray arrayWithObjects:predicate1, predicate2,nil]; } request.predicate=[NSCompoundPredicate andPredicateWithSubpredicates:prepredicateArray]; request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"definition" ascending:YES ]]; self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil]; [self performFetch];} If I understood it correctly, setting request.returnsDistinctResults=YES; should avoid fetching duplicates. However it doesn't work and I'm seeing duplicates of this attribute's value. Is there something I'm missing there? I'd appreciate some pointings there. Thank you in advance. EDIT : If anyone is having the same issue here, after applying David's answer the resulting fetchedResultsController is just a NSDIctionary with object with only the requested value, which for displaying only purposes is quite fine. One thing I've done in cellForRowAtIndexPath in order to display the results on the cell label is: Before : HNMR *hnmr = [self.fetchedResultsController objectAtIndexPath:indexPath];cell.textLabel.text=hnmr.definition; After : cell.textLabel.text=[[self.fetchedResultsController objectAtIndexPath:indexPath] valueForKey:@"definition"];
Now provide the response and nothing else.
| From the documentation of returnsDistinctResults : This value is only used if a value has been set for propertiesToFetch . From the documentation of propertiesToFetch : This value is only used if resultType is set to NSDictionaryResultType . From the documentation of resultType : The default value is NSManagedObjectResultType . This all tells me that the propertiesToFetch is ignored because you haven't set the resultType yourself and the default it to return managed objects instead of dictionaries. Since the propertiesToFetch is ignored the returnsDistinctResults is ignored as well and thus you are still getting duplicates. Try setting the result type to return dictionaries instead of managed objects. request.resultType = NSDictionaryResultType; | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/11233789', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/980841/']} | jdg_70690 |
stackexchange | llm_judgeable_groundtruth_similarity | 10446526 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am working on a C program where I need to get the last modified time of the file. What the program does is a function loops through each file within a directory and when a particular file(s) is found it calls another function to check that the last modified times of the file. Within the directory there is a mylog.txt.1 , mylog.txt.2 and mylog.txt.3 etc. When I list the directory in linux using the ll command I can see that mylog.txt.1 and mylog.txt.2 were modified on the 4th May and mylog.txt.3 was modified on the 3rd May. When the program checks each of these files however, it is always returning 3rd may. Below is the code that I am using. void getFileCreationTime(char *filePath){ struct stat attrib; stat(filePath, &attrib); char date[10]; strftime(date, 10, "%d-%m-%y", gmtime(&(attrib.st_ctime))); printf("The file %s was last modified at %s\n", filePath, date); date[0] = 0;} I've tried all the different variations of st_ctime , i.e. st_mtime and st_atime but they all return 3rd may. Thanks for any help you can provide.
Now provide the response and nothing else.
| This is one of those cases where timezones matter. You're getting gmtime of the st_mtime . You should instead be using localtime viz. strftime(date, 20, "%d-%m-%y", localtime(&(attrib.st_ctime))); this is because ls uses your timezone information, and when you used gmtime as part of the display, it deliberately omitted any timezone information. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/10446526', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/499448/']} | jdg_70691 |
stackexchange | llm_judgeable_groundtruth_similarity | 19367 |
Below is a question asked on the forum serverfault.com. Provide a good and informational response to it like a helpful human would.
Question:
I need to write a script that will build my server from a fresh Ubuntu server install. Among things like Apache and PHP it needs to install MySQL. The only problem here is that when I install MySQL with apt-get, at some point the installation will bring up a dialog that allows me to type my root password. I.e., human interaction is required. How can I bypass this screen during installation and avoid human interaction while still using apt-get to install MySQL?
Now provide the response and nothing else.
| You need to preseed the debconf database. debconf needs to be installed first before you try this. The version of mysql and ubuntu could change the line: echo mysql-server mysql-server/root_password select PASSWORD | debconf-set-selectionsecho mysql-server mysql-server/root_password_again select PASSWORD | debconf-set-selections For example you made need this instead: echo mysql-server-5.0 mysql-server/root_password password PASSWORD | debconf-set-selectionsecho mysql-server-5.0 mysql-server/root_password_again password PASSWORD | debconf-set-selections | {} | {'log_upvote_score': 6, 'links': ['https://serverfault.com/questions/19367', 'https://serverfault.com', 'https://serverfault.com/users/1205/']} | jdg_70692 |
stackexchange | llm_judgeable_groundtruth_similarity | 46717898 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm having slow performance issues with Firestore while retrieving basic data stored in a document compared to the realtime database with 1/10 ratio. Using Firestore, it takes an average of 3000 ms on the first call this.db.collection(‘testCol’) .doc(‘testDoc’) .valueChanges().forEach((data) => { console.log(data);//3000 ms later }); Using the realtime database, it takes an average of 300 ms on the first call this.db.database.ref(‘/test’).once(‘value’).then(data => { console.log(data); //300ms later }); This is a screenshot of the network console : I'm running the Javascript SDK v4.50 with AngularFire2 v5.0 rc.2. Did anyone experience this issue ?
Now provide the response and nothing else.
| UPDATE: 12th Feb 2018 - iOS Firestore SDK v0.10.0 Similar to some other commenters, I've also noticed a slower response on the first get request (with subsequent requests taking ~100ms). For me it's not as bad as 30s, but maybe around 2-3s when I have good connectivity, which is enough to provide a bad user experience when my app starts up. Firebase have advised that they're aware of this "cold start" issue and they're working on a long term fix for it - no ETA unfortunately. I think it's a separate issue that when I have poor connectivity, it can take ages (over 30s) before get requests decide to read from cache. Whilst Firebase fix all these issues, I've started using the new disableNetwork() and enableNetwork() methods (available in Firestore v0.10.0) to manually control the online/offline state of Firebase. Though I've had to be very careful where I use it in my code, as there's a Firestore bug that can cause a crash under certain scenarios. UPDATE: 15th Nov 2017 - iOS Firestore SDK v0.9.2 It seems the slow performance issue has now been fixed. I've re-run the tests described below and the time it takes for Firestore to return the 100 documents now seems to be consistently around 100ms. Not sure if this was a fix in the latest SDK v0.9.2 or if it was a backend fix (or both), but I suggest everyone updates their Firebase pods. My app is noticeably more responsive - similar to the way it was on the Realtime DB. I've also discovered Firestore to be much slower than Realtime DB, especially when reading from lots of documents. Updated tests (with latest iOS Firestore SDK v0.9.0): I set up a test project in iOS Swift using both RTDB and Firestore and ran 100 sequential read operations on each. For the RTDB, I tested the observeSingleEvent and observe methods on each of the 100 top level nodes. For Firestore, I used the getDocument and addSnapshotListener methods at each of the 100 documents in the TestCol collection. I ran the tests with disk persistence on and off. Please refer to the attached image, which shows the data structure for each database. I ran the test 10 times for each database on the same device and a stable wifi network. Existing observers and listeners were destroyed before each new run. Realtime DB observeSingleEvent method: func rtdbObserveSingle() { let start = UInt64(floor(Date().timeIntervalSince1970 * 1000)) print("Started reading from RTDB at: \(start)") for i in 1...100 { Database.database().reference().child(String(i)).observeSingleEvent(of: .value) { snapshot in let time = UInt64(floor(Date().timeIntervalSince1970 * 1000)) let data = snapshot.value as? [String: String] ?? [:] print("Data: \(data). Returned at: \(time)") } }} Realtime DB observe method: func rtdbObserve() { let start = UInt64(floor(Date().timeIntervalSince1970 * 1000)) print("Started reading from RTDB at: \(start)") for i in 1...100 { Database.database().reference().child(String(i)).observe(.value) { snapshot in let time = UInt64(floor(Date().timeIntervalSince1970 * 1000)) let data = snapshot.value as? [String: String] ?? [:] print("Data: \(data). Returned at: \(time)") } }} Firestore getDocument method: func fsGetDocument() { let start = UInt64(floor(Date().timeIntervalSince1970 * 1000)) print("Started reading from FS at: \(start)") for i in 1...100 { Firestore.firestore().collection("TestCol").document(String(i)).getDocument() { document, error in let time = UInt64(floor(Date().timeIntervalSince1970 * 1000)) guard let document = document, document.exists && error == nil else { print("Error: \(error?.localizedDescription ?? "nil"). Returned at: \(time)") return } let data = document.data() as? [String: String] ?? [:] print("Data: \(data). Returned at: \(time)") } }} Firestore addSnapshotListener method: func fsAddSnapshotListener() { let start = UInt64(floor(Date().timeIntervalSince1970 * 1000)) print("Started reading from FS at: \(start)") for i in 1...100 { Firestore.firestore().collection("TestCol").document(String(i)).addSnapshotListener() { document, error in let time = UInt64(floor(Date().timeIntervalSince1970 * 1000)) guard let document = document, document.exists && error == nil else { print("Error: \(error?.localizedDescription ?? "nil"). Returned at: \(time)") return } let data = document.data() as? [String: String] ?? [:] print("Data: \(data). Returned at: \(time)") } }} Each method essentially prints the unix timestamp in milliseconds when the method starts executing and then prints another unix timestamp when each read operation returns. I took the difference between the initial timestamp and the last timestamp to return. RESULTS - Disk persistence disabled: RESULTS - Disk persistence enabled: Data Structure: When the Firestore getDocument / addSnapshotListener methods get stuck, it seems to get stuck for durations that are roughly multiples of 30 seconds. Perhaps this could help the Firebase team isolate where in the SDK it's getting stuck? | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/46717898', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/7254333/']} | jdg_70693 |
stackexchange | llm_judgeable_groundtruth_similarity | 908626 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I know that the natural log of any positive algebraic number is transcendental, as a consequence of the Lindemann-Weierstrass theorem, but what about the natural log of the square root of two (which is irrational). Is this rational or irrational?
Now provide the response and nothing else.
| Not only is $\ln(\sqrt{2})$ irrational, but it's also transcendental! Proof: $$\Large \ln(\sqrt{2})=\ln(2^{1/2})=\frac{1}{2} \underbrace{\ln(2)}_{\in \mathbb{T}}$$ which is transcendental. $\square$ To see why the product of a transcendental number and a non-zero algebraic number is transcendental, see this . For reference, $\mathbb{T}$ is the set of transcendental numbers. | {} | {'log_upvote_score': 5, 'links': ['https://math.stackexchange.com/questions/908626', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/164061/']} | jdg_70694 |
stackexchange | llm_judgeable_groundtruth_similarity | 9840675 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have two strings String s1="426F62";String s2="457665"; The strings are in hex representation. I want to XOR them. XORing normally character by character gives the correct result for others except F XOR 6 .(It gives 112, the answer should be 9) Please tell me the correct way to implement it in JAVA EDIT: Converting to int and xoring works. But how to xor when two strings are of different length.
Now provide the response and nothing else.
| Rather than XORing the Unicode representations, just convert each character into the number it represents in hex, XOR those, then convert it back to hex. You can still do that one character at a time: public String xorHex(String a, String b) { // TODO: Validation char[] chars = new char[a.length()]; for (int i = 0; i < chars.length; i++) { chars[i] = toHex(fromHex(a.charAt(i)) ^ fromHex(b.charAt(i))); } return new String(chars);}private static int fromHex(char c) { if (c >= '0' && c <= '9') { return c - '0'; } if (c >= 'A' && c <= 'F') { return c - 'A' + 10; } if (c >= 'a' && c <= 'f') { return c - 'a' + 10; } throw new IllegalArgumentException();}private char toHex(int nybble) { if (nybble < 0 || nybble > 15) { throw new IllegalArgumentException(); } return "0123456789ABCDEF".charAt(nybble);} Note that this should work however long the strings are (so long as they're the same length) and never needs to worry about negative values - you'll always just get the result of XORing each pair of characters. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/9840675', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/808203/']} | jdg_70695 |
stackexchange | llm_judgeable_groundtruth_similarity | 523430 |
Below is a question asked on the forum serverfault.com. Provide a good and informational response to it like a helpful human would.
Question:
I can use takeown.exe to give the currently logged in user ownership of a folder. But when I try: takeown /s jimswork8 /u Everyone /f c:\test /R /D Y It just gives ownership to the currently logged in user. I CAN do it if I use the UI, so I would think it is possible, but I just can't get the syntax right. Thanks
Now provide the response and nothing else.
| takeown is a leftover from the days when Microsoft insisted you couldn't set the ownership of a file to someone other than the person logged on. I don't know why the tool lets you specify a username, but it will not honor it as far as I know. icacls will allow you to set the owner from the command line. But it will not update ACEs. If the file/folder is simply inheriting permissions, following the /setowner command with a /reset command will fix the ACEs. | {} | {'log_upvote_score': 4, 'links': ['https://serverfault.com/questions/523430', 'https://serverfault.com', 'https://serverfault.com/users/6350/']} | jdg_70696 |
stackexchange | llm_judgeable_groundtruth_similarity | 7411974 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I know that a void method does not return any value, but I can still write code like void nothingDohere() {return;} So, How can "void" work with the "return" statement here?
Now provide the response and nothing else.
| A return statement without a value can only be used in a void method (or a constructor), and simply performs the "get out of the method now" part of returning. Think of a return-with-value statement has having two purposes: Terminating execution of the current method (via finally blocks of course) Making a value computed in the method available to the caller The return statement in a void method simply achieves the first of these; the second makes no sense in a void method. From section 14.17 of the Java Language Specification: A return statement with no Expression must be contained in the body of a method that is declared, using the keyword void, not to return any value (§8.4), or in the body of a constructor (§8.8). A compile-time error occurs if a return statement appears within an instance initializer or a static initializer (§8.7). A return statement with no Expression attempts to transfer control to the invoker of the method or constructor that contains it. To be precise, a return statement with no Expression always completes abruptly, the reason being a return with no value. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/7411974', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/452680/']} | jdg_70697 |
stackexchange | llm_judgeable_groundtruth_similarity | 28213328 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm using Boto to try to get a bucket in Amazon S3, but it returns Bad Request when I use get_bucket() for some of the buckets. I'm starting to wonder if this is a bug with Boto, since I can get the bucket using get_all_buckets(). >>> from boto.s3.connection import S3Connection>>> conn = S3Connection(S3_ACCESS_KEY, S3_SECRET_KEY)>>> buckets = conn.get_all_buckets()>>> buckets[<Bucket: mysite-backups>]>>> buckets[0]<Bucket: mysite-backups>>>> conn.get_bucket('mysite-backups')Traceback (most recent call last): File "<console>", line 1, in <module> File "/path/to/virtualenv/lib/python2.7/site-packages/boto/s3/connection.py", line 502, in get_bucket return self.head_bucket(bucket_name, headers=headers) File "/path/to/virtualenv/lib/python2.7/site-packages/boto/s3/connection.py", line 549, in head_bucket response.status, response.reason, body)S3ResponseError: S3ResponseError: 400 Bad Request>>> conn.create_bucket('mysite_mybucket')<Bucket: mysite_mybucket>>>> conn.get_bucket('mysite_mybucket')<Bucket: mysite_mybucket> This seems to be an issue even if I log in with the same user account as I'm using the access creds for and create it from within the AWS console. Any idea why this might be happening?
Now provide the response and nothing else.
| Turns out the issue is because of the region (I was using Frankfurt). Two ways of dealing with it: Give up on Frankfurt (@andpei points out there are issues currently reported with it ) and recreate the bucket in a different region. Specify the region using the 'host' parameter when connecting (thanks @Siddarth): >>> REGION_HOST = 's3.eu-central-1.amazonaws.com'>>> conn = S3Connection(S3_ACCESS_KEY, S3_SECRET_KEY, host=REGION_HOST)>>> conn.get_bucket('mysite-backups')<Bucket: mysite-backups> You can find the relevant region host here . | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/28213328', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1005499/']} | jdg_70698 |
stackexchange | llm_judgeable_groundtruth_similarity | 102627 |
Below is a question asked on the forum mathematica.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
In the mathematica document "tutorial/CompilingWolframLanguageExpressions" 1 It says about how to set return type of a called function you used in Compile . Clear[com]com[i_] := Binomial[2 i, i]test=Compile[{x, {i, _Integer}}, x^com[i], {{com[_], _Integer}}] From the above example, we can see that because the com function evaluates to integer, so we set {{com[_], _Integer}} to let Compile know the return type of com . But if you inspect it further Needs["CompiledFunctionTools`"]CompilePrint[test] You can see there is MainEvaluate when calling function com . So, I don't understand the meaning of this example in the document. If a compiled function has a MainEvaluate process, then I think compiling it is just nonsense, for it won't speed up things, right? 2 Then I came up with another question, it is also mentioned in the same document page. If we compile Sqrt as below sqrtcom1 = Compile[{{x, _Real}}, Sqrt[x]] we will run into problems if we evaluate sqrtom1[-1.] , it will give errors like CompiledFunction::cfn: Numerical error encountered at instruction 1; proceeding with uncompiled evaluation. >> This is because the return type of Sqrt is assumed to be real by default. This can be see from In[20]:= ToCompiledProcedure[sqrtcom1][[4]]Out[20]= CompiledResult[Register[Real, 1]] So, theoretically we could solve this by sqrtcom2 = Compile[{{x, _Real}}, Sqrt[x], {{Sqrt[_], _Complex}}] But this is not working!! ToCompiledProcedure[sqrtcom2][[4]] still gives CompiledResult[Register[Real, 1]] and sqrtcom2 still gives errors. Why is it not working?
Now provide the response and nothing else.
| Let me counter Daniel Lichtblau's answer This has zero to do with type inferencing. by saying, the example in the tutorial you linked is all about type inference. It is not about compiling com to make it faster. It is about helping the compiler to deduce the correct type for the expression. You have to understand one thing: Highlevel Mathematica language is untyped, which means that it is not known upfront whether Sqrt[x] is an integer, a real, a complex or whether it stays as a general expression. It all depends on the value that x has. Compiled code is completely different, because all variables will have a type. Either explicitly given by you, or derived/assumed by the compiler. Therefore, your first question is not about whether or not com inside the compile will be too slow. The question is, can the compiler derive the type of com and therefore assume a correct return type. Since this example does work correctly even without the explicit type hint, let me give a different example. Here, realf is a function that returns a real number, when the input is an integer. In Mathematica 10.3, this leads to an error message: realf[i_] := 1.5*i;f1 = Compile[{{i, _Integer}}, realf[i]] Calling f1[3] will give you a warning, saying that realf will be the reason that the uncompiled version of f1 is used. If you check the f1 with CompilePrint you will find the line I1 = MainEvaluate[ Hold[realf][ I0]] The important part is that I1 means integer register . So because Compile has no information about realf , it assumes this call will be of type integer which is wrong. If we change the definition to f2 = Compile[{{i, _Integer}}, realf[i], {{realf[_], _Real}}] and check the compiled code again, we see that now a real register is used for the result of realf . R0 = MainEvaluate[ Hold[realf][ I0]] Therfore, f2[3] will run without message since the types are consistent. Nevertheless, realf will be an external call that is evaluated by the kernel. What Daniel's answer is showing you is, that in the specific example of com being defined as Binomial , you can expand the call and indeed compile all instructions to gain a lot of speed. As for your second example, Compile[{{x, _Real}}, Sqrt[x]] there is one additional thing to note: You call Sqrt[x] where x is the input of type Real . Therefore, the compiler deduces that you want the square-root that works on reals. It seems, not even the type hint at the end of Compile prevents this, but there is a simpler solution: sqrtHal = Compile[{{x, _Real}}, Module[{xx = 0. I}, xx = x; Sqrt[xx] ]] Look what we did: we created another variable xx and by giving an initial complex value, we force the type-system to assume xx to be complex. The rest works like in most programming languages. When we assign xx=x a type-conversion takes place and xx is still complex where the imaginary part is zero and the real part is x . Furthermore, the correct complex Sqrt function is selected and therefore sqrtHal[-1](* 0. + 1. I *) works without problems. As soon as you have understood the reasons behind this, you easily find another solution: sqrtHal2 = Compile[{{x, _Real}}, Sqrt[x + 0. I] ] | {} | {'log_upvote_score': 4, 'links': ['https://mathematica.stackexchange.com/questions/102627', 'https://mathematica.stackexchange.com', 'https://mathematica.stackexchange.com/users/4742/']} | jdg_70699 |
stackexchange | llm_judgeable_groundtruth_similarity | 413220 |
Below is a question asked on the forum mathoverflow.net. Provide a good and informational response to it like a helpful human would.
Question:
I am working on $\mathbb{Z}/18\mathbb{Z}$ elliptic curves over cubic fields. The curves are created using the formulas on p. 584 of D. Jeon, C. H. Kim, Y. Lee, Families of elliptic curves over cubic number fields with prescribed torsion subgroups , Mathematics of Computation, V. 80, 273, January 2011, p. 579-591, JSTOR: 41104715 . My code snippet with the saved output for Magma Calculator online is available for download from MEGA. I observe that the following triples of rational $t$ -values produce curves with similar characteristics: $$t_1=t$$ $$t_2=1-\frac{1}{t_1}=1-\frac{1}{t}$$ $$t_3=1-\frac{1}{t_2}=\frac{1}{1-t}$$ For a triple $t_1,t_2,t_3$ , the three elliptic curves are different over three different cubic fields, with different discriminants and conductors. But the ranks, $j$ -invariants, and heights of all generators are the same (e.g., for rank $2$ there will be height $h_1$ for generators $g_{11}, g_{12}, g_{13}$ and height $h_2$ for generators $g_{21}, g_{22}, g_{23}$ , where $g_{ik}$ is the $i$ -th generator for the curve created using $t_k$ ). It was also pretty straightforward to derive the formula for the $j$ -invariant and see that it is always rational: $$j=\frac{(t^3-3t^2+1)^3(t^9-9t^8+27t^7-48t^6+54t^5-45t^4+27t^3-9t^2+1)^3}{(t^3-6t^2+3t+1)(t^2-t+1)^3(-1+t)^9t^9}$$ Magma is unable to check whether the curves are isomorphic, as they are defined over different cubic fields: >> IsIsomorphic(E1, E2); ^Runtime error in 'IsIsomorphic': Curves must be defined over the same base ring Isogeneity check is unavailable over number fields (only over rationals or finite fields): >> IsIsogenous(E1, E2); ^Runtime error in 'IsIsogenous': Bad argument typesArgument types given: CrvEll[FldNum[FldRat]], CrvEll[FldNum[FldRat]] The curves seem to be essentially the same (not distinct in any real sense) to me, even though they might not be considered isomorphic and/or isogenous. Question 1: Does there exist a proper mathematical name for "essentially the same" used above, or the name for the observed connection between the curves? Question 2: Is it possible to map a generator discovered on one of the curves to the other two curves? The explicit expression for the map is not a priority yet. Question 3: If the height of the generator (but not the generator itself) is considered to be known, is it possible to speed up a search process for it? If so, how? Rationale for Questions 2 and 3: It is very easy to determine both generators (with heights $1.798$ and $11.652$ , default Effort := 1 in $45$ seconds) for $t_1=\frac{1}{5}$ , harder to do so for $t_2=-4$ ( Effort := 1000 helps, takes much longer), and very hard to recover the second generator for $t_3=\frac{5}{4}$ ( Effort := 1600 fails).
Now provide the response and nothing else.
| We already have an accepted answer, but since i had already started an answer and was at the half of the route beyond getting the essence of the structure, i completed it now, since it may be useful in similar contexts. On the mathematical side the situation is as follows, recalled for the convenience of the reader from the literature.Notations are as in the already cited paper: Families of Elliptic Curves over Cubic Number Fields with Prescribed Torsion Subgroups, Daeyeol Jeon, Chang Heon Kim, And Yoonjin Lee A further reference that should not be omitted is: Markus Reichert, Explicit Determination of Nontrivial Torsion Structures of Elliptic Curves Over Quadratic Number Fields In order to produce an example of a curve $E$ with torsion $\Bbb Z/18$ , the Ansatz is to work with the Tate normal form, consider curves $E=E(b,c)$ parametrized by twoalgebraic numbers $b,c$ from a cubic number field $K$ , $$E = E(b, c)\ :\qquad y^2 + (1 − c)xy − by = x^3 − bx^2\ ,$$ and arrange that the point $P = (0, 0)$ has order $18$ . For this, pick two parameters $(U,V)$ satisfying the equation for $X_1(18)$ : $$\begin{aligned}X_1(18) \ :\qquad g_{18}(U,V) &= 0\ ,\qquad\text{ where}\\g_{18}(U,V) &:=(U-1)^2 V^2 - (U^3 - U + 1)V + U^2(U - 1) \\&= U^3(1-V) + U^2 (V^2 -1) + U(V-2V^2) + (V^2-V)\\&\sim_{\Bbb Q(V)^\times}U^3 - U^2(V + 1) + \frac{2V^2-V}{V-1} -V\ .\ .\end{aligned}$$ Seen as a polynomial in $U$ , it has degree $3$ .We set $V=t$ to be a "suitable" rational number,and the polynomial $g_{18}(U,t)$ defines a cubic field $K=\Bbb Q(\alpha_t)$ generated by some $\alpha_t$ . Let me plot the connection to $X_1(18)$ explicitly: $$g_{18}(\alpha_t,t)=0\ .$$ Then the formulas for $b,c$ are given by one and the samerational function in $(U,V)=(\alpha_t,t)$ . They are: $$\begin{aligned}b(U,V) &=-\frac{V(U - V)(U^2 + V)(U^2 -UV + V)}{(U^2 -V^2+V)(U^2 + UV -V^2 + V)^2}\ ,\\c(U,V) &=-\frac{V(U - V)(U^2 -UV + V)}{(U^2 -V^2+V)(U^2 + UV -V^2 + V)}\ .\end{aligned}$$ Warming up. We proceed as follows in the given context from above.We fix some $t$ . To have a concrete example, $t$ may be specialized to $t=t_1=1/5$ , as the OP does it also. Let $t'$ be its cousin, $$t'=t_3=\frac 1{ 1-t }\ .$$ We build the corresponding field $K=\Bbb Q(\alpha)$ , where $\alpha =\alpha_t$ is a suitable root of the polynomial $g_{18}(U,t)$ , seen as a polynomial in $U$ . Let $K'=\Bbb Q(\alpha')$ be the cousin field, where $\alpha'$ is a specific root for $g_{18}(U, t')$ . Question: Are $K$ and $K'$ isomorphic (for some good choice of $\alpha'$ )? Answer: Yes, they are, take $\displaystyle \alpha'= 1-\frac 1\alpha$ . To illustrate the situation, we consider first the sample case $t=1/5$ . Sage gives this information as follows: def g18(U, V): return (U^3*V - U^2*V^2 - U^3 + 2*U*V^2 + U^2 - U*V - V^2 + V)R.<U> = PolynomialRing(QQ)t1 = 1/5a1 = g18(U, t1).roots(ring=QQbar, multiplicities=False)[0]t3 = 1/(1 - t1)a3 = 1 - 1/a1print(f'g18(a3, t3) = {g18(a3, t3)}') The sage interpreter gives after a copy+paste of the above code, together with one more line to be sure we get a clean zero: g18(a3, t3) = 0.?e-17sage: g18(a3, t3).minpoly()x Because of the rôle of $(\alpha,t)$ as a special value for $(U,V)$ ,i will use below rather $(u,v)$ pairs instead. Now the whole context can be explained structurally as follows. Proposition: Let $F$ be a field (of characteristic $\ne 2,3$ ).For two parameters $b,c\in F$ , $b\ne 0$ , let $E_T(b,c)$ be the elliptic curve in Tate normal form $$E_T(b, c)\ :\qquad y^2 +(1-c)xy -by = x^3 bx^2\ ,$$ so that $P=(0,0)$ is a rational point on it. For suitable ( $\Delta(A,B)\ne 0$ ) parameters $A,B\in F$ let consider also the elliptic curve in short Weierstrass form $$E_W(A,B)\ :\qquad y^2 = x^3 + Ax+B\ .$$ Fix $u,v$ în $F$ , $u\ne 1$ , so that the pair $(u,v)$ corresponds to a point on the moduli space $X_1(18)$ parametrizedas mentioned above, i.e. it satisfies $$g_{18}(u,v)=0\ ,\qquad\text{ where }\\g_{18}(U,V)=(U-1)^2 V^2 -(U^3 -U + 1)V + U^2(U - 1)\ .$$ Then the pair $(u',v')$ with components $$\begin{aligned}u' &= \frac 1{1-u}\ ,\\v' &= 1-\frac 1v\ ,\end{aligned}$$ is also defining a pointin the moduli space $X_1(18)$ ,i.e. $g_{18}(u',v')=0$ . Let $\underline A$ , $\underline B$ be the rational functions given by $$\begin{aligned}\underline A(b,c) &= -\frac 1{48}\Big(\ ((c-1)^2 - 4b)^2 - 24b(c - 1)\ \Big)\ ,\\\underline B(b,c) &= \frac 1{864}\Big(\ ((c-1)^2 - 4b)^3 - 36b(c-1)^3 + 72b^2(2c + 1)\ \Big)\ .\end{aligned}$$ Consider with a slight abuse of notation $b,c\in F$ and $b',c'\in F$ , then $A,B\in F$ and $A',B'\in F$ as follows $$\begin{aligned}b &= b(u,v)\ ,\qquad &b' &= b(u',v')\ ,\\c &= c(u,v)\ ,\qquad &c' &= c(u',v')\ ,\\[2mm]A &= \underline A(b,c)\ ,\qquad &A' &=\underline A(b',c')\ ,\\B &= \underline B(b,c)\ ,\qquad &B' &=\underline B(b',c')\ ,\\[2mm]&\qquad\text{ and consider the elliptic curves}\\[2mm]E_T &= E(b, c)\ , \qquad &E'_T &= E_T(b', c')\\E_W &= E(A, B)\ , \qquad &E'_W &= E_W(A', B')\ .\end{aligned}$$ Then $$\frac {A'}A = U^{12}\ ,\qquad\frac {B'}B = U^{18}\ ,$$ so the elliptic curves $E_W$ and $E_W'$ are canonically isomorphic via a map $\Phi$ , as shown in the diagram below. The functions $\underline A$ , $\underline B$ were chosen to make $E_T(b,c)$ isomorphic $E_W(A,B)$ . Then the following diagram is commutative: $\require{AMScd}$ $$\begin{CD}E_T @>{\cong}>> E_W\\@A{\cong} AA @A\cong A\Phi A\\E'_T @>>\cong> E'_W\end{CD}$$ So we can compare the rational points $P=(0,0)\in E_T(F)$ and $P'=(0,0)\in E'_T(F)$ in one or any of the common worlds, e.g. in $E_W(F)$ , and then $11P$ and $P'$ (or equivalently $P=5\cdot 11 P$ and $5P'$ ) correspond to one and the same torsion point of order (dividing) $18$ . In a diagram: $\require{AMScd}$ $$\begin{CD}P_T @>{\cong}>> P_W=5\Phi(P'_W)=\Phi(5P'_W)\\@. @A\cong A\Phi A\\5P'_T @>>\cong> 5P'_W\end{CD}$$ Proof by computer. $\square$ Code for the proof. First let us define the needed functions, and needed objects. def bmap(U, V): return -(U^2 - U*V + V) * (U^2 + V) * (U - V) * V / (U^2 + U*V - V^2 + V)^2 / (U^2 - V^2 + V) def cmap(U, V): return -(U^2 - U*V + V) * (U - V) * V / (U^2 + U*V - V^2 + V) / (U^2 - V^2 + V)def Amap(b, c): return -1/48 * ( ((c-1)^2 - 4*b)^2 - 24*b*(c - 1) )def Bmap(b, c): return 1/864 * ( ((c-1)^2 - 4*b)^3 - 36*b*(c-1)^3 + 72*b^2*(2*c + 1) )def f(U, V): return (U^3*V - U^2*V^2 - U^3 + 2*U*V^2 + U^2 - U*V - V^2 + V)R.<U,V> = PolynomialRing(QQ)Q = R.quotient( f(U, V) )FR = R.fraction_field()FQ = Q.fraction_field()u1, v1 = FQ(U), FQ(V)u2, v2 = 1/(1 - u1), 1 - 1/v1 Now we can check: print(f'Is f(u2, v2) zero? {bool( f(u2, v2) == 0 )}' )b , c = bmap(U , V ), cmap(U , V )b1, c1 = bmap(u1, v1), cmap(u1, v1)b2, c2 = bmap(u2, v2), cmap(u2, v2)A , B = Amap(b , c ), Bmap(b , c )A1, B1 = Amap(b1, c1), Bmap(b1, c1)A2, B2 = Amap(b2, c2), Bmap(b2, c2)print(f'Is A2/A1 = u1^12? {bool( A2/A1 == u1^12 )}')print(f'Is B2/B1 = u1^18? {bool( B2/B1 == u1^18 )}')ET = EllipticCurve(FR, [1 - c, -b, -b, 0, 0])EW = EllipticCurve(FR, [A, B])phi = ET.isomorphism_to( EW )PT = ET.point( (0, 0, 1) )PW = phi( PT )five_PW = 5*PWx_PW , y_PW = PW.xy()x_five_PW, y_five_PW = five_PW.xy()x_PW.subs({U: u1, V:v1}) == x_five_PW.subs({U: u2, V: v2}) / u1^6y_PW.subs({U: u1, V:v1}) == y_five_PW.subs({U: u2, V: v2}) / u1^9 This gives the needed confirmations: Is f(u2, v2) zero? TrueIs A2/A1 = u1^12? TrueIs B2/B1 = u1^18? TrueTrueTrue The last two True values confirm that the coordinates of $P=(0,0)=E_T(F)$ and $5P'$ where $P'=(0,0)\in E_T'$ are the same, when transported to $E_W(F)$ . Note: Unfortunately, sage cannot build the needed curves over FQ . | {} | {'log_upvote_score': 4, 'links': ['https://mathoverflow.net/questions/413220', 'https://mathoverflow.net', 'https://mathoverflow.net/users/95511/']} | jdg_70700 |
stackexchange | llm_judgeable_groundtruth_similarity | 28914283 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
What's the difference between these 2 piece of codes? <?php $object1 = new User(); //^^ $object1->name = "Hello"; echo $object1->name; class User {}?> And: <?php $object1 = new User; //^ $object1->name = "Hello"; echo $object1->name; class User {}?> I get the same output: Hello So is there any difference if I use the parentheses or not in: $object1=new User;
Now provide the response and nothing else.
| The are exactly the same, you can compare opcode of these 2 scripts: 1 script: $object1=new User();$object1->name="Hello"; echo $object1->name;class User {} opcode: line # * op fetch ext return operands--------------------------------------------------------------------------------- 3 0 > FETCH_CLASS 4 :0 'User' 1 NEW $1 :0 2 DO_FCALL_BY_NAME 0 3 ASSIGN !0, $1 4 4 ASSIGN_OBJ !0, 'name' 5 OP_DATA 'Hello' 5 6 FETCH_OBJ_R $5 !0, 'name' 7 ECHO $5 6 8 NOP 9 > RETURN 1 2 script: $object1=new User;$object1->name="Hello"; echo $object1->name;class User {} opcode: line # * op fetch ext return operands--------------------------------------------------------------------------------- 3 0 > FETCH_CLASS 4 :0 'User' 1 NEW $1 :0 2 DO_FCALL_BY_NAME 0 3 ASSIGN !0, $1 4 4 ASSIGN_OBJ !0, 'name' 5 OP_DATA 'Hello' 5 6 FETCH_OBJ_R $5 !0, 'name' 7 ECHO $5 6 8 NOP 9 > RETURN 1 | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/28914283', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/3717347/']} | jdg_70701 |
stackexchange | llm_judgeable_groundtruth_similarity | 19151 |
Below is a question asked on the forum cs.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Define the language $L$ as $L = \{a, b\}^* - \{ww\mid w \in \{a, b\}^*\}$. In other words, $L$ contains the words that cannot be expressed as some word repeated twice. Is $L$ context-free or not? I've tried to intersect $L$ with $a^*b^*a^*b^*$, but I still can't prove anything. I also looked at Parikh's theorem, but it doesn't help.
Now provide the response and nothing else.
| It's context-free. Here's the grammar: $S \to A | B|AB|BA$ $A \to a|aAa|aAb|bAb|bAa$ $B \to b|aBa|aBb|bBb|bBa$ $A$ generates words of odd length with $a$ in the center. Same for $B$ and $b$. I'll present a proof that this grammar is correct. Let $L = \{a,b\}^* \setminus \{ww \mid w \in \{a,b\}^*\}$ (the language in the question). Theorem. $L = L(S)$. In other words, this grammar generates the language in the question. Proof. This certainly holds for all odd-length words, since this grammar generates all odd-lengths words, as does $L$. So let's focus on even-length words. Suppose $x \in L$ has even length. I'll show that $x \in L(G)$. In particular, I claim that $x$ can be written in the form $x=uv$, where both $u$ and $v$ have odd length and have different central letters. Thus $x$ can be derived from either $AB$ or $BA$ (according to whether $u$'s central letter is $a$ or $b$). Justification of claim: Let the $i$th letter of $x$ be denoted $x_i$, so that $x = x_1 x_2 \cdots x_n$. Then since $x$ is not in $\{ww \mid w \in \{a,b\}^{n/2}\}$, there must exist some index $i$ such that $x_i \ne x_{i+n/2}$. Consequently we can take $u = x_1 \cdots x_{2i-1}$ and $v = x_{2i} \cdots x_n$; the central letter of $u$ will be $x_i$, and the central letter of $v$ will be $x_{i+n/2}$, so by construction $u,v$ have different central letters. Next suppose $x \in L(G)$ has even length. I'll show that we must have $x \in L$. If $x$ has even length, it must be derivable from either $AB$ or $BA$; without loss of generality, suppose it is derivable from $AB$, and $x=uv$ where $u$ is derivable from $A$ and $v$ is derivable from $B$. If $u,v$ have the same lengths, then we must have $u\ne v$ (since they have different central letters), so $x \notin \{ww \mid w \in \{a,b\}^*\}$. So suppose $u,v$ have different lengths, say length $\ell$ and $n-\ell$ respectively. Then their central letters are $u_{(\ell+1)/2}$ and $v_{(n-\ell+1)/2}$. The fact that $u,v$ have different central letters means that $u_{(\ell+1)/2} \ne v_{(n-\ell+1)/2}$. Since $x=uv$, this means that $x_{(\ell+1)/2} \ne x_{(n+\ell+1)/2}$. If we attempt to decompose $x$ as $x=ww'$ where $w,w'$ have the same length, then we'll discover that $w_{(\ell+1)/2} = x_{(\ell+1)/2} \ne x_{(n+\ell+1)/2} = w'_{(\ell+1)/2}$, i.e., $w\ne w'$, so $x \notin \{ww \mid w \in \{a,b\}^*\}$. In particular, it follows that $x \in L$. | {} | {'log_upvote_score': 6, 'links': ['https://cs.stackexchange.com/questions/19151', 'https://cs.stackexchange.com', 'https://cs.stackexchange.com/users/12256/']} | jdg_70702 |
stackexchange | llm_judgeable_groundtruth_similarity | 423379 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
How do I create or use a global variable inside a function? How do I use a global variable that was defined in one function inside other functions? Failing to use the global keyword where appropriate often causes UnboundLocalError . The precise rules for this are explained at UnboundLocalError on local variable when reassigned after first use . Generally, please close other questions as a duplicate of that question when an explanation is sought, and this question when someone simply needs to know the global keyword.
Now provide the response and nothing else.
| You can use a global variable within other functions by declaring it as global within each function that assigns a value to it: globvar = 0def set_globvar_to_one(): global globvar # Needed to modify global copy of globvar globvar = 1def print_globvar(): print(globvar) # No need for global declaration to read value of globvarset_globvar_to_one()print_globvar() # Prints 1 Since it's unclear whether globvar = 1 is creating a local variable or changing a global variable, Python defaults to creating a local variable, and makes you explicitly choose the other behavior with the global keyword. See other answers if you want to share a global variable across modules. | {} | {'log_upvote_score': 13, 'links': ['https://Stackoverflow.com/questions/423379', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/46646/']} | jdg_70703 |
stackexchange | llm_judgeable_groundtruth_similarity | 16363263 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have 2 kinds of C# WPF app projects: based on .NET 4.0 that I cannot migrate to .NET 4.5 based on .NET 4.0 that I can migrate to .NET 4.5 All of them should spawn 2-10 long-running (days) processes which can be cancelled and re-launched by users. I am interested to follow the best design practices. First of all, now, I am interested to disambiguate about BackgroundWorker usage though, I hope, my question should be valid about other asynchronous patterns. I see (contradicting) concurrent points of view about Asynchronous Programming Model (APM) Event-based Asynchronous Pattern (EAP) BackgroundWorker asynchronous patterns: A) .NET 4.5 made them obsolete named as such in the book By Joseph Albahari, Ben Albahari "C# 5.0 in a Nutshell: The Definitive Reference" in sub-chapter " Obsolete Patterns " while its previous edition ""C# 4.0 in a Nutshell: The Definitive Reference" did not MSDN article "Asynchronous Programming with Async and Await (C# and Visual Basic)" tells: "The async-based approach to asynchronous programming is preferable to existing approaches in almost every case. In particular, this approach is better than BackgroundWorker for IO-bound operations because the code is simpler and you don't have to guard against race conditions. In combination with Task.Run, async programming is better than BackgroundWorker for CPU-bound operations because async programming separates the coordination details of running your code from the work that Task.Run transfers to the threadpool" B) They (or, at least, BackgroundWorker ) are not obsolete in .NET 4.5 I am still in doubt: Are those patterns (first of all, BGW) obsolete in .NET 4.5 ? If they are obsolete in .NET 4.5 why aren't they obsolete in .NET 4.0? 2A) Do I understand incorrectly that .NET 4.5 new features are still "easy" implementable/reproducible in .NET 4.0?
Now provide the response and nothing else.
| I generally recommend Task and/or await if using .NET 4.5. But Task & BGW have 2 distinctly different scenarios. Task is good for general short asynchronous tasks that could be chained to a continuation and await is good at tasks implicitly marshalling back to the UI thread. BGW is good for a single long operation that shouldn't affect the responsiveness of your UI. You can drag-drop a BGW onto design surface and double-click to create event handlers. You don't have to deal with LongRunning or ConfigureAwait if you don't want to marshal to another thread. Many find BGW progress easier than IProgress<T> . Here's some examples of using both in a "lengthy operation" scenario: Since the question specifically mentions .NET 4.0, the following is simple code that uses a Task to do a lengthy operation while providing progress to a UI: startButton.Enabled = false;var task = Task.Factory. StartNew(() => { foreach (var x in Enumerable.Range(1, 10)) { var progress = x*10; Thread.Sleep(500); // fake work BeginInvoke((Action) delegate { progressBar1.Value = progress; }); } }, TaskCreationOptions.LongRunning) .ContinueWith(t => { startButton.Enabled = true; progressBar1.Value = 0; }); Similar code with BackgroundWorker might be: startButton.Enabled = false;BackgroundWorker bgw = new BackgroundWorker { WorkerReportsProgress = true };bgw.ProgressChanged += (sender, args) => { progressBar1.Value = args.ProgressPercentage; };bgw.RunWorkerCompleted += (sender, args) =>{ startButton.Enabled = true; progressBar1.Value = 0;};bgw.DoWork += (sender, args) =>{ foreach (var x in Enumerable.Range(1, 10)) { Thread.Sleep(500); ((BackgroundWorker)sender).ReportProgress(x * 10); }};bgw.RunWorkerAsync(); Now, if you were using .NET 4.5 you could use Progress<T> instead of the BeginInvoke call with Task . And since in 4.5, using await would likely be more readable: startButton.Enabled = false;var pr = new Progress<int>();pr.ProgressChanged += (o, i) => progressBar1.Value = i;await Task.Factory. StartNew(() => { foreach (var x in Enumerable.Range(1, 10)) { Thread.Sleep(500); // fake work ((IProgress<int>) pr).Report(x*10); } }, TaskCreationOptions.LongRunning);startButton.Enabled = true;progressBar1.Value = 0; Using Progress<T> means the code is not coupled to a specific UI framework (i.e. the call to BeginInvoke ) in much the same way that BackgroundWorker facilitates decoupling from a specific UI framework. If you don't care, then you don't need to introduce the added complexity of using Progress<T> As to LongRunning , as Stephen Toub says: "You'd typically only use LongRunning if you found through performance testing that not using it was causing long delays in the processing of other work" so, if you find you need to use it, then you use it--there's the added analysis or just the "complexity" of always adding the LongRunning parameter. Not using LongRunning means the thread pool thread used for the long running operation won't be usable for other, more transient, tasks and could force the thread pool to delay starting one of these transient tasks while it starts up another thread (at least a second). There's no attributes in the framework that specifically say that BGW (or EAP, or APM) are deprecated . So, it's up to you to decide where and when any of these things are "obsolete". BGW in particular always had a very specific usage scenario that still applies to it. You have fairly decent alternatives in .NET 4.0 and 4.5; but I don't really think BGW is "obsolete". I'm not saying always use BackgroundWorker , I'm just saying think before you automatically deprecate BackgroundWorker, in some cases it might be a better choice. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/16363263', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/200449/']} | jdg_70704 |
stackexchange | llm_judgeable_groundtruth_similarity | 7479813 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Hi I've gone through all of the different linkify tutorials I could find but none of them work here is my current code: final SpannableString s = new SpannableString("Please send any questions to [email protected]"); Linkify.addLinks(s, Linkify.EMAIL_ADDRESSES); AlertDialog.Builder builder = new AlertDialog.Builder(Activity.this); builder.setTitle("Warning!") .setMessage(s) .setCancelable(false) .setPositiveButton("Accept", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { } }) .setNegativeButton("Decline", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { Activity.this.finish(); } }).show(); However when I actually run the app it shows the text like blue and underlined as if it were linked but selecting the text doesn't prompt to open the email app. I've also tried with urls and the browser doesn't work is there something that's missing? Thanks for any help.
Now provide the response and nothing else.
| In order to have a clickable area on dialog you need to use TextView (View) and set autoLink=all in layout file or invoke setAutoLinkMask() method from within the code. final SpannableString s = new SpannableString("Please send any questions to [email protected]");//added a TextView final TextView tx1=new TextView(this);tx1.setText(s);tx1.setAutoLinkMask(RESULT_OK);tx1.setMovementMethod(LinkMovementMethod.getInstance());Linkify.addLinks(s, Linkify.EMAIL_ADDRESSES);AlertDialog.Builder builder = new AlertDialog.Builder(this);builder.setTitle("Warning!") .setCancelable(false) .setPositiveButton("Accept", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { } }) .setNegativeButton("Decline", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int id) { finish(); } }) .setView(tx1) .show(); | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/7479813', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/577732/']} | jdg_70705 |
stackexchange | llm_judgeable_groundtruth_similarity | 49157622 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
My service worker is throwing this error in Chrome when I open the WAVE (Web Accessibility Evaluation Tool) extension: Uncaught (in promise) TypeError: Request scheme 'chrome-extension' is unsupported at sw.js:52 (anonymous) @ sw.js:52 Promise.then (async) (anonymous) @ sw.js:50 Promise.then (async) (anonymous) @ sw.js:45 Promise.then (async) (anonymous) @ sw.js:38 My service worker code is: (function () { 'use strict'; var consoleLog; var writeToConsole; const CACHE_NAME = '20180307110051'; const CACHE_FILES = [ 'https://fonts.gstatic.com/s/notosans/v6/9Z3uUWMRR7crzm1TjRicDv79_ZuUxCigM2DespTnFaw.woff2', 'https://fonts.gstatic.com/s/notosans/v6/ByLA_FLEa-16SpQuTcQn4Igp9Q8gbYrhqGlRav_IXfk.woff2', 'https://fonts.gstatic.com/s/notosans/v6/LeFlHvsZjXu2c3ZRgBq9nJBw1xU1rKptJj_0jans920.woff2', 'https://fonts.gstatic.com/s/notosans/v6/PIbvSEyHEdL91QLOQRnZ1xampu5_7CjHW5spxoeN3Vs.woff2', 'https://fonts.gstatic.com/s/materialicons/v22/2fcrYFNaTjcS6g4U3t-Y5ZjZjT5FdEJ140U2DJYC3mY.woff2', 'https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/fonts/fontawesome-webfont.woff2', 'favicon.20180205072319.ico', 'favicons/android-chrome-512x512.20180211120531.png', 'favicons/android-chrome-192x192.20180211120531.png', 'offline.html' ];// for debugging: writeToConsole = false; consoleLog = function (message) { if (writeToConsole) { console.log(message); } };// https://stackoverflow.com/questions/37117933/service-workers-not-updating self.addEventListener('install', function (e) { e.waitUntil( Promise.all([caches.open(CACHE_NAME), self.skipWaiting()]).then(function (storage) { var static_cache = storage[0]; return Promise.all([static_cache.addAll(CACHE_FILES)]); }) ); });// intercept network requests: self.addEventListener('fetch', function (event) { consoleLog('Fetch event for ' + event.request.url); event.respondWith( caches.match(event.request).then(function (response) { if (response) { consoleLog('Found ' + event.request.url + ' in cache'); return response; } consoleLog('Network request for ' + event.request.url);// add fetched files to the cache: return fetch(event.request.clone()).then(function (response) {// Respond with custom 404 page if (response.status === 404) { return caches.match('error?status=404'); } return caches.open(CACHE_NAME).then(function (cache) { if (event.request.url.indexOf('test') < 0) { cache.put(event.request.url, response.clone()); } return response; }).catch(function () { console.log("Uncaught (in promise) TypeError: Request scheme 'chrome-extension' is unsupported"); }); }); }).catch(function (error) {// respond with custom offline page: consoleLog('Error, ' + error);// Really need an offline page here: return caches.match('offline.html'); }) ); });// delete unused caches// https://stackoverflow.com/questions/37117933/service-workers-not-updating self.addEventListener('activate', function (e) { e.waitUntil( Promise.all([ self.clients.claim(), caches.keys().then(function (cacheNames) { return Promise.all( cacheNames.map(function (cacheName) { if (cacheName !== CACHE_NAME) { console.log('deleting', cacheName); return caches.delete(cacheName); } }) ); }) ]) ); });}()); I'm unclear on the nature of the problem and how to correct it. Many thanks in advance for help!
Now provide the response and nothing else.
| WAVE includes some code in your site, which then makes some request to the WAVE extension itself with an url beginning with chrome-extension://xyz. Your service intercepts this request and wants to make a fetch himself because this request is not cached. But urls with the protocol/request scheme chrome-extension:// are not allowed in service worker. So you probably don't want to handle these WAVE requests with your service worker. Skip them with something like if(!event.request.url.startsWith('http')){ //skip request} | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/49157622', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/4557099/']} | jdg_70706 |
stackexchange | llm_judgeable_groundtruth_similarity | 34759845 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Trying to work through an issue with belongsToMany() where my pk is a string (similar to uuid) simple products <-- product_productgroups --> productgroups but products primary key on products is apk varchar(50) when I use integer values, everything is fine, but if I use strings, they are converted to 0 when searching the pivot table: $product = App\Products::with('productgroups')->find('B00AE38KM');"select * from `products` where `products`.`apk` = ? limit 1" array:1 [▼ 0 => "B00AE38KM"] "select productgroups .*, product_productgroup . product_apk as pivot_product_apk , product_productgroup . productgroup_id as pivot_productgroup_id from productgroups inner join product_productgroup on productgroups . id = product_productgroup . productgroup_id where product_productgroup . product_apk in (?)" array:1 [▼ 0 => 0] My Products model has: public function productgroups() { return $this->belongsToMany('App\ProductGroups', 'product_productgroup', 'product_apk', 'productgroup_id'); } TIA!
Now provide the response and nothing else.
| According to docs , you are doing it almost right. You have to create/init Tornado's ioloop with corresponding asyncio, since aiohttp is running on asyncio. from tornado.ioloop import IOLoopimport tornado.webimport tornado.httpserverimport aiohttpfrom tornado.platform.asyncio import AsyncIOMainLoopimport asyncioclass MainHandler(tornado.web.RequestHandler): async def get(self): r = await aiohttp.get('http://google.com/') text = await r.text() self.write("Hello, world, text is: {}".format(text))if __name__ == "__main__": AsyncIOMainLoop().install() app = tornado.web.Application([ (r"/", MainHandler), ]) server = tornado.httpserver.HTTPServer(app) server.bind(1234, '127.0.0.1') server.start() asyncio.get_event_loop().run_forever() The reason why your code get stuck, is that asyncio's ioloop actually is not running, only the Tornado's one, so await is waiting indefinitely. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/34759845', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/495568/']} | jdg_70707 |
stackexchange | llm_judgeable_groundtruth_similarity | 11416959 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have an ASP.NET site that I am trying to access div elements by their ID from the C# code behind file. Essentially I want to see if a div element exists, and if so, alter its properties. I've found many resources out there that point to a dozen different solutions and none of them seem to work. HTML on ASP.Net Page: <div class="contentArea"> <div class="block" id="button1" runat="server"> Some Content Here </div> <div class="block" id="button2" runat="server"> Some Content Here </div> <div class="block" id="button3" runat="server"> Some Content Here </div></div> C# Code Behind (examples I've tried): System.Web.UI.HtmlControls.HtmlGenericControl div1 = (System.Web.UI.HtmlControls.HtmlGenericControl)this.FindControl("button1");div1.Attributes["class"] = "classNameHere"; or Control div1 = this.FindControl("button1");div1.GetType(); When the code gets to the second line of each of the above examples, I get an error: Object reference not set to an instance of an object. If I try the following: if (div1 != null){ // Do Something;} Nothing ever happens because div1 is always set to null. Ironically, if I look at the Locals window and examine this, I can see the button# ids in the listing, so I know they are there, but the system is acting like it isn't finding the control. My ultimate goal is to find the max id # of the button divs (looking at my html example, the max id would be 3 (button3). Maybe there is a better way to go about it, but either way, once I have my max id, I want to be able to touch each div and alter some css properties. Although I could easily do all of this via jQuery, in this instance I need to do this in C#. Any help is much appreciated. If you need more info, let me know. UPDATE I created a new C# web project from scratch. After adding a masterpage (and not altering it) and adding a webform using masterpage, I only added one line to the webform under Content ID="Content2": <div id="button1"></div> From c# code behind I still run into the same exact issue as before. FINAL UPDATE AND ANSWER I'm shocked no one (including myself) caught my mistake from the above update. I never put runat="server" when I created a new project from scratch under the div. Here is how I fixed my problem under my new project from scratch: Add runat="server" to div: <div id="button1" runat="server"></div> Then I did a FindControl on the ContentPlaceHolder under the MasterPage: ContentPlaceHolder myPlaceHolder = (ContentPlaceHolder)Master.FindControl("ContentPlaceHolder1"); Note: This is what the ContentPlaceHolder code looks like on the Site.Master page created by default: <asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server"></asp:ContentPlaceHolder> After finding this ContentPlaceHolder in code behind, I then searched within this placeholder for button1: using System.Web.UI.HtmlControls;HtmlControl myControl = (HtmlControl)myPlaceHolder.FindControl("button1"); Finally I check to see if myControl is null: if (myControl != null){ \\ Do Something} When I ran this code, it found the div I was looking for. Here is the complete code behind all put together: using System.Web.UI.HtmlControls;ContentPlaceHolder myPlaceHolder = (ContentPlaceHolder)Master.FindControl("ContentPlaceHolder1");HtmlControl myControl = (HtmlControl)myPlaceHolder.FindControl("button1");if (myControl != null){ // Do Something}
Now provide the response and nothing else.
| If your page is using a MasterPage, the div control will not be in the main collection of controls. That collection only contains the Content controls pointing to the ContentPlaceholder of your MasterPage. There are three options: Use FindControl on the Content control: contentControl.FindControl("button1"); Do a recursive FindControl until you find the control you need Normally, a declaration of your div control is added to your designer.cs codebehind, so you can directly access the control by its name: button1.Attributes["class"] = "classNameHere"; Update I have created a MasterPage, added a Content Page to it, and added <div id="button1" runat="server">Some text</div> to the Content Page. In the codebehind of my Content Page, I added this code: protected void Page_Load(object sender, EventArgs e){ var control = FindHtmlControlByIdInControl(this, "button1"); if (control != null) { control.Attributes["class"] = "someCssClass"; }}private HtmlControl FindHtmlControlByIdInControl(Control control, string id){ foreach (Control childControl in control.Controls) { if (childControl.ID != null && childControl.ID.Equals(id, StringComparison.OrdinalIgnoreCase) && childControl is HtmlControl) { return (HtmlControl)childControl; } if (childControl.HasControls()) { HtmlControl result = FindHtmlControlByIdInControl(childControl, id); if (result != null) return result; } } return null;} This works for me. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/11416959', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1108806/']} | jdg_70708 |
stackexchange | llm_judgeable_groundtruth_similarity | 14332551 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a fairly large Git repository with 1000s of commits, originally imported from SVN. Before I make my repo public, I'd like to clean up a few hundred commit messages that don't make sense in my new repo, as well as to remove all that git-svn informational text that got added. I know that I can use 'git rebase -i' and then 'git commit --amend' to edit each individual commit message, but with hundreds of messages to be edited, that's a huge pain in the you-know-what. Is there any faster way to edit all of these commit messages? Ideally I'd have every commit message listed in a single file where I could edit them all in one place. Thanks!
Now provide the response and nothing else.
| That's an old question but as there is no mention of git filter-branch , I just add my two cents. I recently had to mass-replace text in commit message, replacing a block of text by another without changing the rest of the commit messages. For instance, I had to replace Refs: #xxxxx with Refs: #22917 . I used git filter-branch like this git filter-branch --msg-filter 'sed "s/Refs: #xxxxx/Refs: #22917/g"' master..my_branch I used the option --msg-filter to edit only the commit message but you can use other filters to change files, edit full commit infos, etc. I limited filter-branch by applying it only to the commits that were not in master ( master..my_branch ) but you can apply it on your whole branch by omitting the range of commits. As suggested in the doc, try this on a copy of your branch.Hope that helps. Sources used for the answer Use case on when to use the function : https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History#The-Nuclear-Option:-filter-branch Function reference (with the list of options) : https://git-scm.com/docs/git-filter-branch Examples of rewrite : https://davidwalsh.name/update-git-commit-messages | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/14332551', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/44003/']} | jdg_70709 |
stackexchange | llm_judgeable_groundtruth_similarity | 33206415 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am making a mining game where if you click somewhere you will delete the block laying there. All blocks right now are just squares and are only drawn if the spot in my 2d boolean array is true. So I am trying to take the position and set it to false wherever you click here is the touchdown method of my inputprocessor private Vector2 tmp = new Vector2();@Overridepublic boolean touchDown(int screenX, int screenY, int pointer, int button) { tmp.x = screenX / MapGrid.CELL_SIZE; tmp.y = screenY / MapGrid.CELL_SIZE; cam.unproject(new Vector3(tmp.x, tmp.y, 0)); grid.manipulateGrid((int)(tmp.x), (int)(tmp.y), false); System.out.println("Clicked at: (" + tmp.x + ", " + tmp.y +")"); return false;} I am also translating the camera to my players position. The grid.manipulateGrid takes an x and a y and sets it to false. My player is located at (10, 126) in grid coordinates and when I click next to him it says I am clicking at (35, 24) I am not sure if I am doing this right but I have been really searching everywhere and can't find a solution. I have found questions similar but to not result. If someone can tell me how to adjust the click to the coordinates of the player I would be incredibly appreciative.
Now provide the response and nothing else.
| What are "unused DT entry" errors? If you have reached this page, it's probably because you have compiled or attempted to run some binaries on your ARM based Android system, with the result that your binary/app crashes or generates a lot of warnings in your logcat . Typically something like this: WARNING: linker: /blahblah/libopenssl.so: unused DT entry: type 0x6ffffffe arg 0x1188 Q: What is a "DT entry"? In a few words, they are descriptive array entries in the file structure of an ELF file. Specifically they are known as Dynamic Array Tags and are requirements for executable and shared objects. However, not all entries are required or available, depending on the processor and kernel architecture. In our case we are faced with a "Warning" that one of these are "unused".What that means is, that your executable or library ( *.so ) files has been compiled with the DT entry indicated, but your kernel is not supporting that entry, for various reasons. The best examples are found on ARM basedAndroid systems, where the system library paths are fixed and the cross compilers used for your firmware (OS/kernel) are set not to use these entries. Usually the binaries still run just fine, but the kernel is flagging this warning every time you're using it. Q: When does this happen? This can happen when: Your ARM kernel is cross-compiled using the wrong flags (usually meant for other processor architectures). Your ARM binaries and libraries are cross-compiled using AOS deprecated compilation flags. and probably other ways yet to be discovered.. Starting from 5.1 (API 22) the Android linker warns about the VERNEED and VERNEEDNUM ELF dynamic sections. The most common flags that cause this error on Android devices are: DT_RPATH 0x0f (15) The DT_STRTAB string table offset of a null-terminated library search path string. This element's use has been superseded by DT_RUNPATH.DT_RUNPATH 0x1d (29) The DT_STRTAB string table offset of a null-terminated library search path string.DT_VERNEED 0x6ffffffe The address of the version dependency table. Elements within this table contain indexes into the string table DT_STRTAB. This element requires that the DT_VERNEEDNUM element also be present.DT_VERNEEDNUM 0x6fffffff The number of entries in the DT_VERNEEDNUM table. Tracking down the error above, we find that this message comes from the bionic library linker.cpp : case DT_VERNEED: verneed_ptr_ = load_bias + d->d_un.d_ptr; break; case DT_VERNEEDNUM: verneed_cnt_ = d->d_un.d_val; break; case DT_RUNPATH: // this is parsed after we have strtab initialized (see below). break; default: if (!relocating_linker) { DL_WARN("\"%s\" unused DT entry: type %p arg %p", get_realpath(), reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val)); } break;} The code (above) supporting this symbol versioning was committed on April 9, 2015 . Thus if your NDK build is either set to support API's earlier than this, or using build tools linking to this earlier library, you will get these warnings. Q: How do I find what DT entries my system or binaries are using? There are many ways to do this: You look into your kernel sources for <linux/elf.h> . You look in your Android NDK installation folders and check: # To find all elf.h files:find /<path_to>/ndk/platforms/android-*/arch-arm*/usr/include/linux/ -iname "elf.h" Do an readelf of your binary: $ readelf --dynamic libopenssl.so Dynamic section at offset 0x23b960 contains 28 entries: Tag Type Name/Value 0x00000003 (PLTGOT) 0x23ce18 0x00000002 (PLTRELSZ) 952 (bytes) 0x00000017 (JMPREL) 0x15e70 0x00000014 (PLTREL) REL 0x00000011 (REL) 0x11c8 0x00000012 (RELSZ) 85160 (bytes) 0x00000013 (RELENT) 8 (bytes) 0x6ffffffa (RELCOUNT) 10632 0x00000015 (DEBUG) 0x0 0x00000006 (SYMTAB) 0x148 0x0000000b (SYMENT) 16 (bytes) 0x00000005 (STRTAB) 0x918 0x0000000a (STRSZ) 1011 (bytes) 0x00000004 (HASH) 0xd0c 0x00000001 (NEEDED) Shared library: [libdl.so] 0x00000001 (NEEDED) Shared library: [libc.so] 0x0000001a (FINI_ARRAY) 0x238458 0x0000001c (FINI_ARRAYSZ) 8 (bytes) 0x00000019 (INIT_ARRAY) 0x238460 0x0000001b (INIT_ARRAYSZ) 16 (bytes) 0x00000020 (PREINIT_ARRAY) 0x238470 0x00000021 (PREINIT_ARRAYSZ) 0x8 0x0000001e (FLAGS) BIND_NOW 0x6ffffffb (FLAGS_1) Flags: NOW 0x6ffffff0 (VERSYM) 0x108c 0x6ffffffe (VERNEED) 0x1188 0x6fffffff (VERNEEDNUM) 2 0x00000000 (NULL) 0x0 As you can see from the error above, the type corresponds to DT_VERNEED . From THIS document: DT_RPATH This element holds the string table offset of a null-terminated search library search path string, discussed in "Shared Object Dependencies." The offset is an index into the table recorded in the DT_STRTAB entry. DT_RPATH may give a string that holds a list of directories, separated by colons (:). All LD_LIBRARY_PATH directories are searched after those from DT_RPATH. Q: So how do you solve or deal with these issues? There are essentially 3 ways to deal with this: the quick the bad the ugly The Quick (you don't have any sources or just can't be bothered) Use an "ELF cleaner" to remove the offending DT entries from a all your binaries. This is an easy and quick remedy, especially when you don't have the sources to recompile them properly for your system. There are at least two cleaners out there that you can use. The Bad (you have the sources) Is the right way to do it, because you'll become a bad-ass ARM cross compiler guru in the process of getting it to work. You basically need to find and tune the compiler settings in the Makefiles used. From here : The Android linker (/system/bin/linker) does not support RPATH or RUNPATH, so we set LD_LIBRARY_PATH=$USR/lib and try to avoid building useless rpath entries with --disable-rpath configure flags. Another option to avoid depending on LD_LIBRARY_PATH would be supplying a custom linker - this is not done due to the overhead of maintaining a custom linker. The Ugly (You just want your app to work with any dirty binary.) You tell your Java app not to freak out when checking for nullin error handlers and instead get fed these warnings, possibly causing fatal exceptions. Use something like: class OpensslErrorThread extends Thread { @Override public void run() { try { while(true){ String line = opensslStderr.readLine(); if(line == null){ // OK return; } if(line.contains("unused DT entry")){ Log.i(TAG, "Ignoring \"unused DT entry\" error from openssl: " + line); } else { // throw exception! break; } } } catch(Exception e) { Log.e(TAG, "Exception!") } }} This is very bad and ugly as it doesn't solve anything, while bloating your code. In addition, the warnings are there for a reason, and that is that in future AOS versions, this will become a full fledged error! Q. What else? Many changes in the API's between 18-25 (J to N) has been made in way the Android kernel and libraries are compiled. I cannotprovide a remotely close explanation of all that, but perhaps thiswill help guide you in the right direction. The best sources is of course looking in the Android sources and documentation itself. For example, HERE or HERE . And finally the full list: Name Value d_un Executable Shared Object---------------------------------------------------------------------------------------------DT_NULL 0 Ignored Mandatory MandatoryDT_NEEDED 1 d_val Optional OptionalDT_PLTRELSZ 2 d_val Optional OptionalDT_PLTGOT 3 d_ptr Optional OptionalDT_HASH 4 d_ptr Mandatory MandatoryDT_STRTAB 5 d_ptr Mandatory MandatoryDT_SYMTAB 6 d_ptr Mandatory MandatoryDT_RELA 7 d_ptr Mandatory OptionalDT_RELASZ 8 d_val Mandatory OptionalDT_RELAENT 9 d_val Mandatory OptionalDT_STRSZ 0x0a (10) d_val Mandatory MandatoryDT_SYMENT 0x0b (11) d_val Mandatory MandatoryDT_INIT 0x0c (12) d_ptr Optional OptionalDT_FINI 0x0d (13) d_ptr Optional OptionalDT_SONAME 0x0e (14) d_val Ignored OptionalDT_RPATH 0x0f (15) d_val Optional OptionalDT_SYMBOLIC 0x10 (16) Ignored Ignored OptionalDT_REL 0x11 (17) d_ptr Mandatory OptionalDT_RELSZ 0x12 (18) d_val Mandatory OptionalDT_RELENT 0x13 (19) d_val Mandatory OptionalDT_PLTREL 0x14 (20) d_val Optional OptionalDT_DEBUG 0x15 (21) d_ptr Optional IgnoredDT_TEXTREL 0x16 (22) Ignored Optional OptionalDT_JMPREL 0x17 (23) d_ptr Optional OptionalDT_BIND_NOW 0x18 (24) Ignored Optional OptionalDT_INIT_ARRAY 0x19 (25) d_ptr Optional OptionalDT_FINI_ARRAY 0x1a (26) d_ptr Optional OptionalDT_INIT_ARRAYSZ 0x1b (27) d_val Optional OptionalDT_FINI_ARRAYSZ 0x1c (28) d_val Optional OptionalDT_RUNPATH 0x1d (29) d_val Optional OptionalDT_FLAGS 0x1e (30) d_val Optional OptionalDT_ENCODING 0x1f (32) Unspecified Unspecified UnspecifiedDT_PREINIT_ARRAY 0x20 (32) d_ptr Optional IgnoredDT_PREINIT_ARRAYSZ 0x21 (33) d_val Optional IgnoredDT_MAXPOSTAGS 0x22 (34) Unspecified Unspecified UnspecifiedDT_LOOS 0x6000000d Unspecified Unspecified UnspecifiedDT_SUNW_AUXILIARY 0x6000000d d_ptr Unspecified OptionalDT_SUNW_RTLDINF 0x6000000e d_ptr Optional OptionalDT_SUNW_FILTER 0x6000000e d_ptr Unspecified OptionalDT_SUNW_CAP 0x60000010 d_ptr Optional OptionalDT_SUNW_SYMTAB 0x60000011 d_ptr Optional OptionalDT_SUNW_SYMSZ 0x60000012 d_val Optional OptionalDT_SUNW_ENCODING 0x60000013 Unspecified Unspecified UnspecifiedDT_SUNW_SORTENT 0x60000013 d_val Optional OptionalDT_SUNW_SYMSORT 0x60000014 d_ptr Optional OptionalDT_SUNW_SYMSORTSZ 0x60000015 d_val Optional OptionalDT_SUNW_TLSSORT 0x60000016 d_ptr Optional OptionalDT_SUNW_TLSSORTSZ 0x60000017 d_val Optional OptionalDT_SUNW_CAPINFO 0x60000018 d_ptr Optional OptionalDT_SUNW_STRPAD 0x60000019 d_val Optional OptionalDT_SUNW_CAPCHAIN 0x6000001a d_ptr Optional OptionalDT_SUNW_LDMACH 0x6000001b d_val Optional OptionalDT_SUNW_CAPCHAINENT 0x6000001d d_val Optional OptionalDT_SUNW_CAPCHAINSZ 0x6000001f d_val Optional OptionalDT_HIOS 0x6ffff000 Unspecified Unspecified UnspecifiedDT_VALRNGLO 0x6ffffd00 Unspecified Unspecified UnspecifiedDT_CHECKSUM 0x6ffffdf8 d_val Optional OptionalDT_PLTPADSZ 0x6ffffdf9 d_val Optional OptionalDT_MOVEENT 0x6ffffdfa d_val Optional OptionalDT_MOVESZ 0x6ffffdfb d_val Optional OptionalDT_POSFLAG_1 0x6ffffdfd d_val Optional OptionalDT_SYMINSZ 0x6ffffdfe d_val Optional OptionalDT_SYMINENT 0x6ffffdff d_val Optional OptionalDT_VALRNGHI 0x6ffffdff Unspecified Unspecified UnspecifiedDT_ADDRRNGLO 0x6ffffe00 Unspecified Unspecified UnspecifiedDT_CONFIG 0x6ffffefa d_ptr Optional OptionalDT_DEPAUDIT 0x6ffffefb d_ptr Optional OptionalDT_AUDIT 0x6ffffefc d_ptr Optional OptionalDT_PLTPAD 0x6ffffefd d_ptr Optional OptionalDT_MOVETAB 0x6ffffefe d_ptr Optional OptionalDT_SYMINFO 0x6ffffeff d_ptr Optional OptionalDT_ADDRRNGHI 0x6ffffeff Unspecified Unspecified UnspecifiedDT_RELACOUNT 0x6ffffff9 d_val Optional OptionalDT_RELCOUNT 0x6ffffffa d_val Optional OptionalDT_FLAGS_1 0x6ffffffb d_val Optional OptionalDT_VERDEF 0x6ffffffc d_ptr Optional OptionalDT_VERDEFNUM 0x6ffffffd d_val Optional OptionalDT_VERNEED 0x6ffffffe d_ptr Optional OptionalDT_VERNEEDNUM 0x6fffffff d_val Optional OptionalDT_LOPROC 0x70000000 Unspecified Unspecified UnspecifiedDT_SPARC_REGISTER 0x70000001 d_val Optional OptionalDT_AUXILIARY 0x7ffffffd d_val Unspecified OptionalDT_USED 0x7ffffffe d_val Optional OptionalDT_FILTER 0x7fffffff d_val Unspecified OptionalDT_HIPROC 0x7fffffff Unspecified Unspecified Unspecified | {} | {'log_upvote_score': 7, 'links': ['https://Stackoverflow.com/questions/33206415', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/5256266/']} | jdg_70710 |
stackexchange | llm_judgeable_groundtruth_similarity | 43633415 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am working with an iOS app which uses both objective-c and swift code. Currently app IPA size became large. Some resources are included but may not be used in Release IPA. I want to find out which resource should be removed and which resource are making my app size increased unnecessarily. I wonder if there is any such tool or xcode profiler to analyze.
Now provide the response and nothing else.
| So far the best tool I found is https://github.com/tinymind/LSUnusedResources LSUnusedResources A Mac App to find unused images and resources in an XCode project. It is heavily influenced by jeffhodnett‘s Unused, but Unused is very slow, and the results are not entirely correct. So It made some performance optimization, the search speed is more faster than Unused. Export unused resource list Use this tool and export unused/unreferenced resource list into unused.txt Remove references from Xcode .pbxproj file Use the below python script to delete references from project.pbxproj file: file = open("unused.txt","r") data = [line.rstrip('\n') for line in open("project.pbxproj", 'r')] newFile = open("project2.pbxproj","w") def removeLine(imageName): temp = data for line_s in temp: if line_s.find(imageName) != -1: data.remove(line_s) else: continue for line in file: if (len(line) > 5): tokens = line.split("/") len_a = len(tokens) imageName = tokens[len_a-1] removeLine(imageName.rstrip('\n')) for line in data: newFile.write(line) newFile.write('\n') And an alternative script, in bash: #!/bin/bash UNUSED_ASSETS_FILENAME="unused-images.txt" XCODEPROJ_PATH="zilly.xcodeproj/project.pbxproj" while read LINE; do FILENAME="$(basename "$LINE")" if [[ $FILENAME =~ (png|jpeg|jpg|gif)$ ]]; then echo "Removing '$FILENAME' references from $XCODEPROJ_PATH" sed -i '' "/$FILENAME/d" $XCODEPROJ_PATH fi done < $UNUSED_ASSETS_FILENAME | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/43633415', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1084174/']} | jdg_70711 |
stackexchange | llm_judgeable_groundtruth_similarity | 213766 |
Below is a question asked on the forum unix.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a source text file containing text where some words are l e t t e r s p a c e d like the word "letterspaced" in this question (i.e., there is a space character between the letters of the word. How can I undo letterspacing using sed? A pattern like \{[A-Za-z] \}+[A-Za-z] captures a letterspaced word, and s/ //g takes the spaces out, but how do I extract a letterspaced word out of a line of text and undo letterspacing without harming the legitimate space characters in the rest of the text?
Now provide the response and nothing else.
| You can do it like this: sed -e's/ \([^ ][^ ]\)/\n\1/g' \ -e's/\([^ ][^ ]\) /\1\n/g' \ -e's/ //g;y/\n/ /' <<\INI have a source text file containing text wheresome words are l e t t e r s p a c e dlike the word "letterspaced" in this question(i.e., there is a space character between theletters of the word. IN The idea is to first find all spaces which are either preceded by or followed by two or more not-space characters and set them aside as newline characters. Next simply remove all remaining spaces. And last, translate all newlines back to spaces. This is not perfect - without incorporating an entire dictionary of every word you could possibly use the best you will get is some kind of heuristic. This one's pretty good, though. Also, depending on the sed you use, you might have to use a literal newline in place of the n I use in the first two substitution statements as well. Aside from that caveat, though, this will work - and work very fast - with any POSIX sed . It doesn't need to do any costly lookaheads or behinds, because it just saves impossibles, which means it can handle all of pattern space for each substitution in a single address. OUTPUT I have a source text file containing text where somewords are letterspacedlike the word "letterspaced" in this question(i.e., there is a space character between theletters of the word. | {} | {'log_upvote_score': 4, 'links': ['https://unix.stackexchange.com/questions/213766', 'https://unix.stackexchange.com', 'https://unix.stackexchange.com/users/65872/']} | jdg_70712 |
stackexchange | llm_judgeable_groundtruth_similarity | 12233406 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
How do you prevent multiple clients from using the same session ID? I'm asking this because I want to add an extra layer of security to prevent session hijacking on my website. If a hacker somehow figures out another user's session ID and makes requests with that SID, how can I detect that there are different clients sharing a single SID on the server and then reject the hijack attempt? EDIT I have accepted Gumbo's answer after careful consideration because I've come to the realization that what I'm asking for is impossible due to the restrictions of a stateless HTTP protocol . I forgot about what is perhaps the most fundamental principle of HTTP, and now that I think about this question seems a bit trivial. Let me elaborate what I mean: After User A logs in on example.com, he is given some random session ID, for simplicity's sake, let it be 'abc123'. This session ID is stored as a cookie on the client side and is validated with a server-side session to ensure the user who logged in remains logged in as he moves from one webpage to another. This cookie of course would not need to exist if HTTP were not stateless. For that reason, if User B steals User A's SID, and creates a cookie on his computer with the value 'abc123', he would have successfully hijacked User A's session, but there is simply no way for the server to legitimately recognize that User B's request is any different from User A's requests, and therefore the server has no reason to reject any request. Even if we were to list the sessions that were already active on the server and try to see if someone is accessing a session that is already active, how can we determine that it is another user who is accessing the session illegitimately and not the same user who is already logged in with a session ID, but simply trying to make another request with it (ie navigate to a different webpage). We can't. Checking the user agent? Can be spoofed - but good as a Defense in Depth measure nevertheless. IP Address? Can change for legitimate reasons - but instead of not checking for the IP address at all, I suggest checking something like the first two octets of the IP, as even a user on a data plan network who constantly has a changing IP for perfectly legitimate reasons would only usually have the last two octets of their IP change. In consclusion, it is the stateless HTTP that condemns us to never being able to fully protect our websites from session hijacking, but good practices (like the ones Gumbo has provided) will be good enough to prevent a good majority of session attacks. Trying to protect sessions from hijacking by denying multiple requests of the same SID is therefore simply ludicrous, and would defeat the whole purpose of sessions.
Now provide the response and nothing else.
| Unfortunately, there is no effective way to unmistakably identify a request that originates from an attacker in opposite to a genuine request. Because most properties that counter measures check like the IP address or user agent characteristics are either not reliable (IP address might change among multiple requests) or can be forged easily (e. g. User-Agent request header) and thus can yield unwanted false positives (i. e. genuine user switched IP address) or false negatives (i. e. attacker was able to successfully forge request with same User-Agent ). That’s why the best method to prevent session hijacking is to make sure an attacker cannot find out another user’s session ID. This means you should design your application and its session management that (1) an attacker cannot guess a valid session ID by using enough entropy, and (2) that there is no other way for an attacker to obtain a valid session ID by known attacks/vulerabilities like sniffing the network communication, Cross-Site Scripting, leakage through Referer , etc. That said, you should: use enough random input for generating the session ID (see session.entropy_file , session.entropy_length , and session.hash_function ) use HTTPS to protect the session ID during transmission store the session ID in a cookie and not in the URL to avoid leakage though Referer (see session.use_only_cookies ) set the cookie with the HttpOnly and Secure attributes to forbid access via JavaScript (in case of XSS vulnerabilities) and to forbid transmission via insecure channel (see session.cookie_httponly and session.cookie_secure ) Besides that, you should also regenerate the session ID while invalidating the old one (see session_regenerate_id function ) after certain session state changes (e. g. confirmation of authenticity after login or change of authorization/privileges) and you can additionally do this periodically to reduce the time span for a successful session hijacking attack. | {} | {'log_upvote_score': 8, 'links': ['https://Stackoverflow.com/questions/12233406', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1576985/']} | jdg_70713 |
stackexchange | llm_judgeable_groundtruth_similarity | 22498767 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
When I compile the below code snippet code in Visual studio 2008, I get this warning. BOOLCPlan::getStandardPlan() const{ return m_standardPlan;}bool m_bStandardPlan;if(plan!=NULL){ // Assign the values to the Cola object poCola->m_lPlanId = plan->getPlanId(); poCola->m_lPlanElementId = plan->getPlanElementId(); poCola->m_lPlanElementBaseId = plan->getPlanElementBaseId(); poCola->m_bStandardPlan = plan->getStandardPlan(); //C4800 return 1;} I referred the following links, http://msdn.microsoft.com/en-us/library/b6801kcy%28v=vs.90%29.aspx Forcing value to boolean: (bool) makes warning, !! doesnt Warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning) I'm not sure how to fix this warnings.
Now provide the response and nothing else.
| BOOL is a typedef for int somewhere in WinAPI. WinAPI is a C API, so they can't use C++'s bool . If you can't get rid of it by returning a bool from the function, e.g. because you don't maintain the function, then you can use an explicit check against zero to get rid of the warning: poCola->m_bStandardPlan = (plan->getStandardPlan() != 0); Another consideration would be to add a function that encapsulates the check: bool getStandardPlan(CPlan const& plan) { return plan->getStandardPlan() != 0;} and then poCola->m_bStandardPlan = getStandardPlan(plan); | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/22498767', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/3360310/']} | jdg_70714 |
stackexchange | llm_judgeable_groundtruth_similarity | 17400617 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I found a very basic code as described below and I cannot get it to work in my c# windows Forms solution. I got the errors: The best overloaded method match for 'System.Enum.TryParse(string, out string)' has some invalid arguments Argument 1: cannot convert from 'System.Type' to 'string' public enum PetType{ None, Cat = 1, Dog = 2}string value = "Dog";PetType pet = (PetType)Enum.TryParse(typeof(PetType), value);if (pet == PetType.Dog){ ...} I don't understand where is the problem. The errors are all on the Enum.TryParse line. Any idea? Thanks.
Now provide the response and nothing else.
| As you can see from the documentation, Enum.TryParse<TEnum> is a generic method that returns a boolean property. You are using it incorrectly. It uses an out parameter to store the result: string value = "Dog";PetType pet;if (Enum.TryParse<PetType>(value, out pet)){ if (pet == PetType.Dog) { ... }}else{ // Show an error message to the user telling him that the value string // couldn't be parsed back to the PetType enum} | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/17400617', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/693560/']} | jdg_70715 |
stackexchange | llm_judgeable_groundtruth_similarity | 8006 |
Below is a question asked on the forum mechanics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a Mitsubishi Lancer (but I don't live in USA, so it's not the same sold in America), and the manual says to inflate tires to 31 psi. Now I'll be replacing my tires with ones from a different brand/model, which is rated by some costumers to be quieter, softer (less vibration from the road transferred to the car) and with a slightly smaller grip (but since I don't use it to the limits, I think it's ok). Since they have some characteristics that are different from the original tire, how much should I inflate? The original recommended pressure (31 psi) applies only to the same tire, or it's a characteristic of the vehicle (and should be used no matter what tire I use) ?
Now provide the response and nothing else.
| tl;dr : The recommended pressure is almost always a good general recommendation. You can make adjustments to suit your specific needs. The original recommended pressure (31 psi) applies only to the same tire, or it's a characteristic of the vehicle (and should be used no matter what tire I use) ? As a first step, I'm going to point you at Tire Rack's excellent discussions on tire pressures and a whole host of other technical topics. 31 psi is a reasonable starting pressure on your vehicle, regardless of the specific tire that you put on it. Let's quickly consider some of the factors that the air in the tires affects: It acts as a spring . We don't drive on solid rubber tires for a reason: these are much more comfortable. It defines the tire's shape . More air => taller tire with a smaller contact patch. Less air => shorter tire with a larger contact patch. It defines the tire's stiffness , especially in terms of the sidewalls. An underinflated tire is going to roll over its sidewall in a hard turn, wearing out the side and edge. A well-inflated tire will hold its shape, keeping a more defined contact patch on the road. Now let's talk about examples of where we'd potentially like to adjust our tire pressures. Note: all of the factors below assume that you're tuning by relatively modest amounts (e.g., plus or minus 10%). So when I say "more air," I don't mean 100psi, and "less air" is not the same as saying "zero air." A front engine car is heavier in the front than it is in the rear. It is common to see a higher tire pressure in the front partially as a consequence of this increased load. Street cars are generally set up with a bias towards understeer. Lower tire pressures in the rear will increase grip on the back end, reducing the chance that it will swing around on a casual driver. A tire is an undamped spring (i.e., no shock absorber). A high tire pressure will transmit more of the bumps and jolts of a lower quality road directly to the driver. This factor increases in importance in proportion to the annoyance of the spouse in the passenger seat. A tire with less air will generally have more grip in all respects. This means that it will feel less responsive to sudden steering adjustments. A small drop (e.g., 2 psi) is common to increase winter traction where real snow accumulation is common and persistant (i.e., not where I live). A severe drop in pressure will cause the sidewalls to bulge out significantly and dramatically increasing the footprint of the tire. This can be used to get out of a deep hole in the snow. You can see a practical example of this technique in the Top Gear Polar Special . A tire with more air will have a smaller contact patch and stiffer sidewalls, generally leading to increased fuel economy. In short, tuning the tire pressures is the absolute cheapest way to adjust your suspension performance. Nitpick: yes, I know that it's not the air alone that's acting as a spring. It's the combination of the air, rubber, belts and the deformation that happens under an impact. For an introductory discussion, though, we can say "air = spring." | {} | {'log_upvote_score': 4, 'links': ['https://mechanics.stackexchange.com/questions/8006', 'https://mechanics.stackexchange.com', 'https://mechanics.stackexchange.com/users/2107/']} | jdg_70716 |
stackexchange | llm_judgeable_groundtruth_similarity | 8120812 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
When using Visual Studio 2008, when I "Publish Web Site", the application builds correctly, but then I get a "Publish failed" message: What possible reasons are there for this, and how can I prevent it?
Now provide the response and nothing else.
| I had the same issue. Nightmare to identify the problem, because the logs and outputs show no errors or failures. I simply get "Build: 39 succeeded" and "Publish: 1 failed". I resolved the problem by systematically removing all NuGet packages one at a time (and removing code that references it) until I identified the offending one. This takes a LONG time! However, the answer for me was Microsoft.Net.Compilers . No idea how I ended up with that in my project, but as soon as I removed that package, everything publishes fine again. Edit - For what it's worth, this problem occurs on VS 2008, 2012 and 2015 but does not occur on 2017. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/8120812', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/370103/']} | jdg_70717 |
stackexchange | llm_judgeable_groundtruth_similarity | 61960657 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I get the error sometimes when downloading a video. For example, I can attempt to download the video and it will download, the next time I run the script that video will not download and the error will be thrown. def search_youtube(song,randomString,playlist_name): results = YoutubeSearch(song, max_results=1).to_dict() for v in results: url = 'https://www.youtube.com' + v['link'] print(url) _filename = song format_input = 'mp4' format_output = 'mp3' print("Downloading...." + ' ' + song) time.sleep(5) YouTube(url).streams.first().download(filename=randomString,output_path=playlist_name)
Now provide the response and nothing else.
| I have just fixed this issue.Follow these steps. Go to pytube directory in site-packages. If you're not sure where full location is use: pip show pytube3 . You'll see location of site-packages. In site-packages/pytube folder opened from above location, you'll see a file called extract.py . Open that file in your IDE or text-editor. You'll see a function called apply_descrambler . Inside that function, in line 301 probably, you'll see something like parse_qs(formats[i]["cipher"]) for i, data in enumerate(formats) Replace cipher in formats[i]["cipher"] with signatureCipher . Thus that line becomes, parse_qs(formats[i]["signatureCipher"]) for i, data in enumerate(formats) pytube3 should work fine now. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/61960657', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/2404688/']} | jdg_70718 |
stackexchange | llm_judgeable_groundtruth_similarity | 35748734 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm trying to make a form get information from the user and use this information to send a email. Here's my code: #forms.pyfrom django import formsclass ContactForm(forms.Form): nome = forms.CharField(required=True) email = forms.EmailField(required=True) msg = forms.CharField( required=True, widget=forms.Textarea )#views.pyfrom django.shortcuts import render, redirect, get_object_or_404, HttpResponseRedirect, render_to_responsefrom django.core.mail import send_mailfrom .forms import ContactFormdef contato(request): form_class = ContactForm if request.method == 'POST': form = form_class(request.POST) if form.is_valid(): nome = request.POST.get('nome') email = request.POST.get('email') msg = request.POST.get('msg') send_mail('Subject here', msg, email, ['[email protected]'], fail_silently=False) return HttpResponseRedirect('blog/inicio') return render(request, 'blog/inicio.html', {'form': form})#contato.html{% extends "blog/base.html" %}{% block content %} <form role="form" action="" method="post"> {% csrf_token %} {{ form.as_p }} <button type="submit">Submit</button> </form>{% endblock %} and when I try to enter in contact page I get this error: local variable 'form' referenced before assignment It is saying tha the error is in this line of views.py: return render(request, 'blog/inicio.html', {'form': form}) I'm a little new on Django, can you please help me?
Now provide the response and nothing else.
| You define the form variable in this if request.method == 'POST': block. If you access the view with a GET request form gets not defined. You should change the view to something like this: def contato(request): form_class = ContactForm # if request is not post, initialize an empty form form = form_class(request.POST or None) if request.method == 'POST': if form.is_valid(): nome = request.POST.get('nome') email = request.POST.get('email') msg = request.POST.get('msg') send_mail('Subject here', msg, email, ['[email protected]'], fail_silently=False) return HttpResponseRedirect('blog/inicio') return render(request, 'blog/inicio.html', {'form': form}) | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/35748734', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/5255892/']} | jdg_70719 |
stackexchange | llm_judgeable_groundtruth_similarity | 1594 |
Below is a question asked on the forum reverseengineering.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I browsed a lot, but can't find any resources for reverse engineering an IPA file (iPhone application). Is there any method to reverse engineer an IPA file to its source? I've tried to rename it to zip and open it via Winrar/Winzip to view its source, but it doesn't seem helpful. What are the possibilities to decompile/reverse engineer an IPA file to its source code?
Now provide the response and nothing else.
| If the IPA file is straight from iTunes/iPhone (without any modification), the code section in the binary (as indicated by the Info.plist) is encrypted with FairPlay (Apple's proprietary DRM). If you are unsure, you can check whether the cryptid bit is set with otool (see this page ). otool -arch armv7 -l thebinary | grep crypt (where thebinary is the executable binary - see the app's Info.plist, CFBundleExecutable key) Pre Decryption: if cryptid is 0, you can proceed on to the Post Decryption section. Otherwise, you will need to decrypt the app. The typical method in brief (with a jailbroken iOS device) is to Install otool, gdb and ldid from Cydia Install the IPA on an authorized device Run otool on the binary to get information such as the size of the encrypted payload Launch the app and suspend it immediately Use gdb to dump the payload (beginning from 0x2000) gdb -p <process id> then dump output.bin 0x2000 0xNNNN where NNNN is the sum of the beginning (0x2000) and the payload size Create a new file, using the first 0x1000 bytes of the original binary, and appended with the dump file Use ldid to sign the new binary, and change the cryptid to 0 (so that iOS won't decrypt the decrypted app again) There are many tools of dubious purposes (piracy) which automates the process, however the above is the gist of how the process is done. Post Decryption: You can begin reverse engineering the code when you have access to an unencrypted copy of the binary. One possible tool is IDA Pro (Free version does not support ARM).It may still be quite messy since much of iOS's code works with objc_sendMsg(). This IDA plugin may help: https://github.com/zynamics/objc-helper-plugin-ida When you are patching functions, an easier way to work (if you know Objective-C) is to use MobileSubstrate to hook the relevant functions. See Dustin Howett's theos if you would like to try this method. Useful Links: More about the decryption process: http://iphonedevwiki.net/index.php/Crack_prevention Getting otool: https://apple.stackexchange.com/questions/21256/i-cant-find-otool-on-my-jailbroken-ipod Signing with ldid (since the original signature is made invalid after editing) http://www.saurik.com/id/8 For newer devices Some of the tools (gdb in my base) are not working reliably on the iPhone 5S / iOS7. Currently a method that works is to use a popular open-source cracking software "Clutch" . The actual cracking process can be found here: https://github.com/KJCracks/Clutch/blob/master/Clutch/Binary.m iOS 11 Bishop Fox's bfdecrypt , used together with their bfinject should work for iOS 11. | {} | {'log_upvote_score': 7, 'links': ['https://reverseengineering.stackexchange.com/questions/1594', 'https://reverseengineering.stackexchange.com', 'https://reverseengineering.stackexchange.com/users/1581/']} | jdg_70720 |
stackexchange | llm_judgeable_groundtruth_similarity | 184748 |
Below is a question asked on the forum mathoverflow.net. Provide a good and informational response to it like a helpful human would.
Question:
This question is related to something that I asked yesterday: If $ F(x,\bullet) \in {L^{\infty}}(G,B) $ for all $ x \in G $, then is $ x \mapsto F(x,\bullet) $ strongly measurable? Pietro Majer provided a non-affirmative answer to the former question by constructing a very elementary counterexample. Let $ (X,\Sigma,\mu) $ be a $ \sigma $-finite measure space and $ B $ a Banach space. A function $ f: X \to B $ is said to be strongly $ \mu $-measurable iff it is the almost-everywhere pointwise limit of a sequence $ (s_{n}: X \to B)_{n \in \mathbb{N}} $ of integrable simple functions, where an integrable simple function $ s: X \to B $ has the form$$s = \sum_{(E,b) \in I} \chi_{E} \cdot b$$for some finite subset $ I $ of $ \{ E \in \Sigma \mid \mu(E) < \infty \} \times B $. Let $ G $ be a second-countable, locally compact Hausdorff group and $ \mu_{G} $ a fixed Haar measure on the Borel $ \sigma $-algebra $ \mathscr{B}(G) $ of $ G $. The second-countability condition implies that $ G $ is $ \sigma $-compact, which ensures that $ (G,\mathscr{B}(G),\mu_{G}) $ is a $ \sigma $-finite measure space. Let $ B $ be a separable Banach space. Let $ {L^{2}}(G,B) $ denote the set of all (equivalence classes of) square-integrable strongly $ \mu_{G} $-measurable functions from $ G $ to $ B $. Note: $ {L^{2}}(G,B) $ is a separable Banach space, as the algebraic tensor product $ {L^{2}}(G) \odot B $ can be seen as a dense and separable linear subspace. Question. If $ F: G \times G \to B $ is a strongly $ \mu_{G \times G} $-measurable function where $ F(x,\bullet) \in {L^{2}}(G,B) $ for all $ x \in G $, then is it true that the mapping \begin{align}G & \to {L^{2}}(G,B); \\x & \mapsto F(x,\bullet)\end{align} is strongly $ \mu_{G} $-measurable? One strategy is to use Pettis’ Measurability Theorem, as considered by myself and also suggested to me by Pietro, to prove that\begin{align}G & \to {L^{2}}(G,B); \\x & \mapsto F(x,\bullet)\end{align}is weakly $ \mu_{G} $-measurable instead. However, the one problem with this is that the dual space of $ {L^{2}}(G,B) $ is hard to visualize. I am actually interested in the case when $ B $ is a separable $ C^{*} $-algebra, which makes $ {L^{2}}(G,B) $ a Hilbert $ B $-module. However, even with this extra bit of structure, it appears difficult to exploit Pettis’ Measurability Theorem due to a lack of understanding of the dual space of $ {L^{2}}(G,B) $. I sincerely appreciate any help because the answers to these questions would help me better understand measurability issues related to the theory of representations of twisted $ C^{*} $-algebraic crossed products on Hilbert $ C^{*} $-modules.
Now provide the response and nothing else.
| The inequality is true, and follows upon integrating by parts. The integral is $$ \int_{k+1/2}^{k+3/2} x d\Big( -\frac{\log (1+2 e^{2\pi t} \cos(2\pi x) +e^{4\pi t}}{4\pi e^{2\pi t}} \Big) $$and integration by parts gives$$= \frac{1}{4\pi e^{2\pi t}} \int_{k+1/2}^{k+3/2} \log \frac{1+2e^{2\pi t} \cos (2\pi x) + e^{4\pi t}}{1-2e^{2\pi t} +e^{4\pi t}} dx.$$Using $\log (1+y) \le y$, the above is $$ \le \frac{1}{4\pi e^{2\pi t}} \int_{k+1/2}^{k+3/2} \frac{(2+2\cos(2\pi x))e^{2\pi t}}{(1-e^{2\pi t})^2} dx = \frac{1}{2\pi} \frac{1}{(1-e^{2\pi t})^2}. $$ | {} | {'log_upvote_score': 4, 'links': ['https://mathoverflow.net/questions/184748', 'https://mathoverflow.net', 'https://mathoverflow.net/users/50614/']} | jdg_70721 |
stackexchange | llm_judgeable_groundtruth_similarity | 8317295 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am trying to convert 65529 from an unsigned int to a signed int . I tried doing a cast like this: unsigned int x = 65529;int y = (int) x; But y is still returning 65529 when it should return -7. Why is that?
Now provide the response and nothing else.
| It seems like you are expecting int and unsigned int to be a 16-bit integer. That's apparently not the case. Most likely, it's a 32-bit integer - which is large enough to avoid the wrap-around that you're expecting. Note that there is no fully C-compliant way to do this because casting between signed/unsigned for values out of range is implementation-defined. But this will still work in most cases: unsigned int x = 65529;int y = (short) x; // If short is a 16-bit integer. or alternatively: unsigned int x = 65529;int y = (int16_t) x; // This is defined in <stdint.h> | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/8317295', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/680441/']} | jdg_70722 |
stackexchange | llm_judgeable_groundtruth_similarity | 11596 |
Below is a question asked on the forum stats.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Especially in the computer-science oriented side of the machine learning literature, AUC (area under the receiver operator characteristic curve) is a popular criterion for evaluating classifiers. What are the justifications for using the AUC? E.g. is there a particular loss function for which the optimal decision is the classifier with the best AUC?
Now provide the response and nothing else.
| For binary classifiers $C$ used for ranking (i.e. for each example $e$ we have $C(e)$ in the interval $[0, 1]$) from which the AUC is measured the AUC is equivalent to the probability that $C(e_1) > C(e_0)$ where $e_1$ is a true positive example and $e_0$ is a true negative example. Thus, choosing a model with the maximal AUC minimizes the probability that $C(e_0) \geq C(e_1)$. That is, minimizes the loss of ranking a true negative at least as large as a true positive. | {} | {'log_upvote_score': 5, 'links': ['https://stats.stackexchange.com/questions/11596', 'https://stats.stackexchange.com', 'https://stats.stackexchange.com/users/3567/']} | jdg_70723 |
stackexchange | llm_judgeable_groundtruth_similarity | 44671457 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
As per the Spring documantation : Add this annotation to an @Configuration class to have the SpringSecurity configuration defined in any WebSecurityConfigurer or morelikely by extending the WebSecurityConfigurerAdapter base class andoverriding individual methods: Or As this @EnableWebSecurity depicts, is used to enable SpringSecurity in our project. But my question is that even if I don't annotate any of my class with @EnableWebSecurity still the application prompting for username and password.(default behaviour) So I am receiving the same behaviour with @EnableWebSecurity and without @EnableWebSecurity . Can someone please explain what exactly is this annotation for?
Now provide the response and nothing else.
| The @EnableWebSecurity is a marker annotation. It allows Spring to find (it's a @Configuration and, therefore, @Component ) and automatically apply the class to the global WebSecurity . If I don't annotate any of my class with @EnableWebSecurity still the application prompting for username and password. Yes, it is the default behavior. If you looked at your classpath, you could find other classes marked with that annotation (depends on your dependencies): SpringBootWebSecurityConfiguration ; FallbackWebSecurityAutoConfiguration ; WebMvcSecurityConfiguration . Consider them carefully, turn the needed configuration off, or override its behavior. | {} | {'log_upvote_score': 7, 'links': ['https://Stackoverflow.com/questions/44671457', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/4516110/']} | jdg_70724 |
stackexchange | llm_judgeable_groundtruth_similarity | 42873 |
Below is a question asked on the forum electronics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
Many modern appliances use a 5V Power connection. Internally they are working with 3.3V. Wouldn't it be easier to have 5V everywhere? Examples are many USB devices or Routers (they use 5V for power but 3.3V for serial communication).
Now provide the response and nothing else.
| 5 V became much used in early logic families, and especially TTL. While TTL is very much passé now everybody still talks about "TTL levels". (I even hear UART decribed as "TTL bus", which is a misnomer: it's a logic level communication channel, but may well be a different voltage than 5 V.) In TTL 5 V was a good choice for the setpoints of the BJTs and for a high noise immunity. The 5 V level was retained when technology switched to HCMOS (High-Speed CMOS), with 74HC as the best-known family; 74HCxx ICs can operate at 5 V, but the 74HCT is TTL-compatible for its input levels as well. That compatibility may be required in mixed technology circuits, and that's the reason why 5 V won't be completely abandoned soon. But HCMOS doesn't need the 5 V like TTL's bipolar transistors did. A lower voltage means lower power consumption: an HCMOS IC at 3.3 V will typically consume 50 % or less power than the same circuit at 5 V. So you create a microcontroller which internally runs at 3.3 V to save power, but has 5 V I/Os. (The I/O may also be 5 V-tolerant; then it works at the 3.3 V levels, but won't be damaged by 5 V on its inputs. Next to compatibility 5 V also offers a better noise immunity. And it goes further. I've worked with ARM7TDMI controllers (NXP LPC2100) with a core running on 1.8 V, with 3.3 V I/Os. The lower voltage is an extra power saving (only 13 % of a 5 V controller), and lower EMI as well. The drawback is that you need two voltage regulators. So that's the trend: internally ever lower voltages for lower power consumption and EMI, and externally a higher voltage for better noise immunity and connectivity. | {} | {'log_upvote_score': 6, 'links': ['https://electronics.stackexchange.com/questions/42873', 'https://electronics.stackexchange.com', 'https://electronics.stackexchange.com/users/13964/']} | jdg_70725 |
stackexchange | llm_judgeable_groundtruth_similarity | 122307 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
This isn't really a GCD question, because GCD is only defined for integers. I'm interested in the the existence of a common divisor of any two non-zero real numbers. In other words can you prove or disprove the following: Given $x,y \neq 0\in \mathbb{R}, \exists \space g \space s.t. \space x/g \in \mathbb{Z}$ and $y/g \in \mathbb{Z}$. (I hope my math is understandable, haven't done this in awhile). It's clearly possible for many numbers, including irrational ones (e.g. for multiples of $\pi$, $g = \pi$). Is it possible for all real numbers?
Now provide the response and nothing else.
| The following conditions are equivalent for nonzero reals $x,y$ There is a real $g$ such that $x/g$ and $y/g$ are integers The quotient $x/y$ is rational Proof: $1 \implies 2$: Since quotient of integers is rational, your condition implies that $(x/g) / (y/g) \in \mathbb{Q}$ after clearing $g$ in denominators $x/y \in \mathbb{Q}$. $2 \implies 1$: If $x/y$ is rational: $x/y=p/q$ then define $g = y/q$ (or $g = x/p$), then $x/g = xq/y = p$ and $y/g = q$ are integers. QED So any pair of reals with irrational quotient is a counterexample, for example $x=1$ and $y=\sqrt{2}$. Real numbers $x,y$ with rational quotient are known as commensurable . This is how irrationality was formulated in the ancient times. It has been said that diagonal of a square is not commensurable with its side. The Euclidean algorithm for finding GCD was originally formulated on segments (reals) - it found a common measure ($g$) given segments of length $x$ and $y$. | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/122307', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/27242/']} | jdg_70726 |
stackexchange | llm_judgeable_groundtruth_similarity | 737632 |
Below is a question asked on the forum physics.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I did some classical approximations of the Navier Stokes equations, fluid is: non-viscous incompressible irrotational When are these approximations wrong? and particularly is there a "general method" to evaluate in a theoretical way "the error" of an approximation?For example, for a given fluid with a given velocity flow, what will be the order of the terms that I neglect? I see some methods using dimensionnal analysis, but it wasn't very clear for me...
Now provide the response and nothing else.
| Fluid dynamics has developed a systematic method to easily identify the correct approximations pertaining to different regimes. It is based on a set of dimensionless numbers expressing the typical ratio between different terms in Navier-Stokes, and related equations for the dynamics of fluids. The basic idea is that using typical lengths, velocities, times, etc., as units for the physical quantities appearing in the equations, it is possible to understand which terms can be neglected as a first approximation and possibly be re-introduced in a perturbative way, if necessary. I suggest you refer to this Wikipedia page for starting information and quite an extensive list of possible dimensionless numbers. Here I'll briefly illustrate the technique with an example.Let's assume that we want to understand when finite compressibility plays a role in fluid dynamics. We can start with an equation containing density ( $\rho$ ) variation and the velocity field ( ${\bf u}$ ), the continuity equation: $$\frac{\partial \rho}{\partial t}+\nabla\cdot \left( {\rho \bf u} \right)=0.$$ By introducing the material derivative ( $\frac{D}{Dt}$ ) and the equation of state to use pressure as a variable, it may be rewritten as $$\frac{1}{\rho c^2}\frac{Dp}{Dt}+\nabla \cdot {\bf u}=0, \tag{1}$$ where $c$ is the speed of sound. At this point, we can introduce a typical length ( $L$ ), a typical speed of the fluid ( $U$ ), and a typical density ( $\bar\rho$ ), and we can use them as new units. Equation ( $1$ ) becomes: $$\frac{U^2}{\rho^* c^2}\frac{Dp^*}{Dt^*}+\nabla \cdot {\bf u}^*=0, \tag{2}$$ where $$\begin{align}t^* &= \frac{Ut}{L}\\{\bf u}^*&=\frac{{\bf u}}{U}\\p^*&=\frac{p}{\bar\rho U^2}\\\rho^*&=\frac{\rho}{\bar \rho}\end{align}$$ and, by introducing the dimensionless Mach number $M=\frac{U}{c}$ , we get $$\frac{M^2}{\rho^*}\frac{Dp^*}{Dt^*}+\nabla \cdot {\bf u}^*=0, \tag{2}$$ Therefore, the importance of finite compressibility is encoded in the value of the dimensionless Mach's number. When it is negligible, the flow behaves as incompressible ( $\nabla \cdot {\bf u}^* = 0$ ). If it is large, spatio-temporal variations of density cannot be neglected. Moreover, one could systematically introduce their effect perturbatively. However, we have to take into account that one requires some care from the mathematical point of view since the limit $M \rightarrow 0$ is non-trivial, changing the character of the resulting differential equations (see, for instance, the topic singular perturbation on Wikipedia). | {} | {'log_upvote_score': 5, 'links': ['https://physics.stackexchange.com/questions/737632', 'https://physics.stackexchange.com', 'https://physics.stackexchange.com/users/288840/']} | jdg_70727 |
stackexchange | llm_judgeable_groundtruth_similarity | 272102 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
The situation is this: I have a homogeneous ideal with many generators and variables, too many to simply ask isPrime I in Macaulay2. However, the ideal simplifies significantly when localizing in each variable (that is, setting one of the variables equal to one and substitute everywhere for lone variables). It turns out, when localized in each variable, the ideal $I_{(x_i)}$ is prime. The question is, when can I conclude that the ideal itself is prime? I cannot in general do this, because there are examples of rings with all localizations integral domains, but not the ring itself (take for example $\mathbb{Z}/(6)$ and localize in only two primes to get $\mathbb{Z}/(3)$ and $\mathbb{Z}/(2)$). In my case, the ideal is $I \subseteq k[x_1,\cdots, x_{20}]$, with $k$ an algebraically closed field of characteristic zero (or just $\mathbb{C}$). Thinking about this, it seems that if there are "sufficiently many prime ideals", then it is true that locally prime implies prime, but I have not been able to prove this.
Now provide the response and nothing else.
| Despite of the counterexamples, there are still some hopes. And if you are interested, here is a simple criterion. Let $k$ be a field. Let $I$ be a homogeneous ideal of $k[x_0, \dots, x_n]$ such that $I_{(x_i)}$ is prime for all $i\le n$ . Then $I$ is prime if and only if $I_{(x_ix_j)}$ is a proper ideal for all $i, j\le n$ . Geometrically, let $Z=V_+(I)$ , then the last condition is $Z\cap D_+(x_ix_j)\ne\emptyset$ for all $i,j$ . Proof. As $Z$ is already reduced, we only have to care about the irreducibility of $Z$ . If $Z$ is irreducible, then $Z\cap D_+(x_i)$ and $Z\cap D_+(x_j)$ are both non-empty (because $I_{(x_i)}$ is a proper ideal defining $Z\cap D_+(x_i)$ ) hence dense open subsets of $Z$ , so their interseciton $Z\cap D_+(x_ix_j)\ne \emptyset$ . Conversely, suppose the above condition holds. Let $F$ be an irreducible component of $Z$ . We can suppose $F\cap D_+(x_0)\ne \emptyset$ . Then $Z\cap D_+(x_0)=F\cap D_+(x_0)$ because $Z\cap D_+(x_0)$ is irreducible. For any $i\le n$ , by hypothesis $Z\cap D_+(x_0x_i)$ is a non-empty open subset of $Z\cap D_+(x_0)=F\cap D_+(x_0)$ , so it is dense and contained in $F$ . But it is also dense in $Z\cap D_+(x_i)$ for the same reason. Therefore $Z\cap D_+(x_i)\subseteq F$ . This being true for all $i\le n$ , we have $Z=F$ and $Z$ is irreducible. Edit This is in fact a general result. Let $X$ be a topological space and let $Z$ be a closed (or even an arbitrary) subset of $X$ such that there exists an open covering $\{ U_i\}_i$ of $X$ with $Z\cap U_i$ irreducible (in particular non-empty) for all $i$ . Then $Z$ is irreducible if and only if $Z\cap U_i\cap U_j\ne\emptyset$ for all $i,j$ . The proof is the same as above. | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/272102', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/4284/']} | jdg_70728 |
stackexchange | llm_judgeable_groundtruth_similarity | 8088108 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am aware that Ini Files are meant for single lines of information, needless to say I am trying to read/write multi lines to and from the Ini - without much success (I always seem to do things the hard way!) Lets say my Ini File when saved, looks like this: [richardmarx] Filenames=hazardchildren of the nightright here waiting Suppose the Ini File is built dynamically (ie, the richardmarx and the Filenames are not know, but unique - they could literally be anything). How would I be able to read the Ini File? In this example then, how could I put richardmarx into a TEdit, and the Filenames associated with richardmarx section into a memo? Many thanks in advance.
Now provide the response and nothing else.
| Do not store multi-line strings into an INI file to begin with. Escape the line breaks, like @RobertFrank suggested. I would not use an asterik for that, though, as that is a valid text character. I would use something like this instead: [richardmarx] Filenames=hazard%nchildren of the night%nright here waiting You can then read the string and replace the %n sequences with the value of the sLineBreak global variable. If you needed to store an actual % character, escape it as %% , eg: [sales] value=Sale! 50%% off%nat Macy's | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/8088108', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/-1/']} | jdg_70729 |
stackexchange | llm_judgeable_groundtruth_similarity | 1057224 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
$$\lim_{n\to \infty}\int_0^\pi\frac{\sin\left(nx\right)}{1+x^2}dx=0 $$ I consider if it can be solved by other methods without Riemann lemma.I try my best to do it as follow: Let $t=nx$ $$\lim_{n\to \infty}\int_0^\pi\frac{\sin\left(nx\right)}{1+x^2}dx$$ \begin{eqnarray} &=&\lim_{n\to \infty}\int_0^{n\pi}\frac{\sin\left(t\right)}{1+(\frac{t}{n})^2}d\frac{t}{n}\\&=&\lim_{n\to \infty}\int_0^{n\pi}\frac{n\sin\left(t\right)}{n^2+t^2}dt\\&=&\lim_{n\to \infty}\sum_{k=0}^{k=n-1}\int_{k\pi}^{(k+1)\pi}\frac{n\sin\left(t\right)}{n^2+t^2}dt\\\end{eqnarray} Then I can not go on. Who can tell me how to prove it? Thank you.
Now provide the response and nothing else.
| Integration by parts is enough: $$\int_{0}^{\pi}\frac{\sin(nx)}{1+x^2}\,dx =\left.\frac{\frac{1}{n}(1-\cos(nx))}{1+x^2}\right|_{0}^{\pi}+\frac{1}{n}\int_{0}^{\pi}\frac{2x\,(1-\cos(nx))}{(1+x^2)^2}\,dx,\tag{1}$$so:$$\left|\int_{0}^{\pi}\frac{\sin(nx)}{1+x^2}\,dx\right|\leq\frac{1}{n}\left(\frac{2}{\pi^2+1}+\frac{2\pi^2}{\pi^2+1}\right)=\frac{2}{n}.\tag{2}$$Using the Cauchy-Schwarz inequality to bound the second integral in $(1)$, it is possible to improve the last inequality up to:$$\left|\int_{0}^{\pi}\frac{\sin(nx)}{1+x^2}\,dx\right|\leq\frac{1}{n}\left(\frac{2}{\pi^2+1}+\sqrt{\frac{3\pi}{2}\int_{0}^{\pi}\frac{4x^2}{(1+x^2)^4}\,dx}\right)<\frac{14}{9n}.\tag{3}$$ | {} | {'log_upvote_score': 5, 'links': ['https://math.stackexchange.com/questions/1057224', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/196699/']} | jdg_70730 |
stackexchange | llm_judgeable_groundtruth_similarity | 13598682 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am displaying the fields in the temlate like this <div> Name </div> <div> {{ form.status }} </div><div> Name </div> <div> {{ form.name }} </div><div> Description{{ form.description }} </div><div> Sub category{{ form.subcategory }} </div> Now i want to have the div box where i can display all erros related all fields whether hidden or not something like {{ form.errors }} is it possible
Now provide the response and nothing else.
| - AtomicInteger is used to perform the atomic operation over an integer , its an alternative when you don't want to use synchronized keyword. - Using a volatile on a Non-Atomic field will give inconsistent result. int volatile count;public void inc(){count++} - static will make a variable shared by all the instances of that class , But still it will produce an inconsistent result in multi-threading environment. So try these when you are in multithreading environment: 1. Its always better to follow the Brian's Rule: When ever we write a variable which is next to be read by another thread, or when we are reading a variable which is written just by another thread, it needs to be synchronized. The shared fields must be made private, making the read and write methods/atomic statements synchronized. 2. Second option is using the Atomic Classes , like AtomicInteger, AtomicLong, AtomicReference, etc. | {} | {'log_upvote_score': 6, 'links': ['https://Stackoverflow.com/questions/13598682', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/767244/']} | jdg_70731 |
stackexchange | llm_judgeable_groundtruth_similarity | 219487 |
Below is a question asked on the forum stats.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
With my limited understanding of the logistic regression, I understand that the coefficients in logistic regression are the odds ratios.Does it make send to normalize them (divide each one over the overall sum)? I guess NO, can anyone explain why?in this case is there a way to relate the different predictors' coefficients to have a comparative understanding?
Now provide the response and nothing else.
| The short answer is that normalizing the coefficients will not affect the predictions, but it will mess up the estimated class probabilities. Don't do it. The coefficients don't represent the odds ratios but rather the feature weights . They can be negative. If a coefficient is strongly positive, it means that the corresponding feature is very much correlated with the positive class. If it is strongly negative, then its means that the feature is strongly correlated with the negative class. If the coefficient is close to zero, then it means that the feature is not correlated much with either the positive or the negative class. So if you want to compare the importance of each feature, you should compare the absolute values of the coefficients (and you can normalize them just for convenience, if you want, but don't use these normalized absolute coefficients to make predictions, only use them to compare feature importance). ( Edit : this assumes that the features have been normalized prior to training) This is probably all you need to know. Read on if you want to understand what would happen if you tried to normalize the coefficients. The decision function for logistic regression is: $h_\mathbf{\theta}(\mathbf{x}) = \sigma(\sum\limits_{i=0}^{n}\theta_i x_i)$ where $\sigma(t) = \dfrac{1}{1 + \exp(-t)}$ (the logistic function ) and $\mathbf{\theta}$ is the parameter vector, and $\mathbf{x}$ is the feature vector (including a bias term $x_0 = 1$) and $n$ is the number of features. The model's prediction $\hat{y}$ for the instance $\mathbf{x}$ is given by: $\hat{y} =\begin{cases} 0 & \text{ if }h_\mathbf{\theta}(\mathbf{x}) < 0.5\\ 1 & \text{ if }h_\mathbf{\theta}(\mathbf{x}) \ge 0.5\end{cases}$ Notice that $\sigma(t) \ge 0.5$ when $t \ge 0$, and $\sigma(t) < 0.5$ when $t < 0$ so the prediction simplifies to: $\hat{y} =\begin{cases} 0 & \text{ if }\sum\limits_{i=0}^{n}\theta_i x_i < 0\\ 1 & \text{ if }\sum\limits_{i=0}^{n}\theta_i x_i \ge 0\end{cases}$ If you normalize the feature vector, you get the new parameter vector $\bar{\mathbf{\theta}} = \dfrac{\mathbf{\theta}}{K} $. Since the coefficients can be negative, it would not make sense to divide them by the sum of coefficients (the sum could be negative or zero). So instead, let's define $K$ as the range of values (anyway, even if you choose another method for normalization, it does not change what follows). $K = \underset{i}\max(\theta_i) - \underset{i}\min(\theta_i)$ Look at what happens to the sum used for predictions: $\sum\limits_{i=0}^{n}\bar{\theta}_i x_i = \sum\limits_{i=0}^{n}\dfrac{\theta_i}{K} x_i = \dfrac{1}{K}\sum\limits_{i=0}^{n}\theta_i x_i$ Everything just got multiplied by the constant $\dfrac{1}{K}$. If $K > 0$, the predictions don't change a bit, since $\dfrac{1}{K} \sum\limits_{i=0}^{n}\theta_i x_i$ has the same sign as $\sum\limits_{i=0}^{n}\theta_i x_i$. If $K = 0$ (which can only happen if all coefficients are equal), then $K$ is not defined (you can't normalize the coefficients). If you use another normalization technique, and end up with $K<0$, then all predictions get reversed, which is probably not a good idea! So normalizing the coefficients (by dividing them by their range of values) will not affect predictions. However, it will mess up the decision function $h_\mathbf{\theta}$. This function is used to estimate the probability of the positive class. By multiplying all coefficients by $\dfrac{1}{K}$, you will end up making the same predictions (since the sign is not affected), but the estimated probability will be higher or lower depending on the value of $K$. For example, if $K = 2$ then: $h_\mathbf{\bar{\theta}}(\mathbf{x}) = \sigma(\sum\limits_{i=0}^{n}\bar{\theta}_i x_i) = \sigma\left(\dfrac{1}{2} \sum\limits_{i=0}^{n}\theta_i x_i\right)$ This can't be simplified much: if you plot the curve of $\sigma(t)$ and compare it to $\sigma(\frac{1}{2}t)$, you will find that this updated model will be much less confident about its predictions. For no good reason. | {} | {'log_upvote_score': 4, 'links': ['https://stats.stackexchange.com/questions/219487', 'https://stats.stackexchange.com', 'https://stats.stackexchange.com/users/95087/']} | jdg_70732 |
stackexchange | llm_judgeable_groundtruth_similarity | 1711787 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
These are two problems which I have been trying to solve. The arithmetic mean of twin primes 5 and 7 is 6 which is a triangular number. Do there exist any other such twin primes? If they exist find a pair otherwise prove that there do not exist any other such twin primes. Let the smaller prime be $p$. The larger one is $p+2$. Their mean is $p+1$. Triangular numbers are of the form $\frac{n(n+1)}{2}$. So, $$\frac{p+p+2}{2} = \frac{n(n+1)}{2}$$ How do I proceed further? The arithmetic mean of twin primes 3 and 5 is 4 which is a perfect square. Do there exist any other such twin primes? If they exist find a pair otherwise prove that there do not exist any other such twin primes. I have made no progress in this one. Thanks.
Now provide the response and nothing else.
| On the first one: $$p+1 = \frac{n(n+1)}{2}$$$$p = \frac{n(n+1)}{2} - 1$$$$p = \frac{(n^2 + n - 2)}{2}$$$$p = \frac{(n-1)(n+2)}{2}$$ Since $p$ is prime, $(n-1)/2 = 1$, so $n=3$ and $p+1 = n(n-1)/2 = 3*4/2 = 6$; or $n-1 = 1$ so $p+1 = 3$ (which, when we go back and check, is not a solution as $p+2 = 4$ and we're looking at twin primes). This proves $p+1 = 6$ is the only average of twin primes that is a triangular number. On the second one: $$p+1 = n^2$$$$p = n^2 - 1$$$$p = (n-1)(n+1)$$ Since $p$ is prime, $n-1 = 1$. This yields $p+1 = n^2 = 2^2 = 4$. This proves $p+1 = 4$ is the only average of twin primes that is a perfect square. | {} | {'log_upvote_score': 4, 'links': ['https://math.stackexchange.com/questions/1711787', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/255473/']} | jdg_70733 |
stackexchange | llm_judgeable_groundtruth_similarity | 10294629 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have GPS Tracking application main goal is saving GPS coordinate to backed database every 5 minutes interval. So i created Service & receiver because even my my application doesn't open / run this should work. After user enter executive code , it create database and go to welcome screen. In there it start GPS capturing & save it to PDA database calling service to upload. I have receiver, when phone is Booted it start this receiver & receiver call service. My problem is receiver doesn't call service. It didn't go to Service class. protected void onStop(){ super.onStop(); if(gpsReceiver != null){ unregisterReceiver(gpsReceiver); }} @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.home); gpsReceiver = new GpsReceiver(); IntentFilter intentFilter1 = new IntentFilter(Intent.ACTION_BOOT_COMPLETED); intentFilter1.addAction(Intent.ACTION_BOOT_COMPLETED); intentFilter1.addAction(Intent.ACTION_POWER_CONNECTED); intentFilter1.addAction(Intent.ACTION_SCREEN_ON); registerReceiver(gpsReceiver, intentFilter1); locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locationManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, MINIMUM_TIME_BETWEEN_UPDATES, MINIMUM_DISTANCE_CHANGE_FOR_UPDATES, new MyLocationListener() ); locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, new MyLocationListener()); } private class MyLocationListener implements LocationListener { public void onLocationChanged(Location location) { String message = String.format( "Location \n Longitude: %1$s \n Latitude: %2$s", location.getLongitude(), location.getLatitude()); longitude = location.getLongitude(); latitude =location.getLatitude(); //save GPS coordinate to PDA DB GPSDBAdapter dbAdapter = GPSDBAdapter.getDBAdapterInstance(HomeActivity.this); dbAdapter.openDataBase(); dbAdapter.insertGPS(longitude, latitude, "MASS", deserializeObject()); dbAdapter.close(); //After save GPS coordinate it upload to backend using service startService(new Intent(HomeActivity.this, UploadService.class)); Toast.makeText(HomeActivity.this, message, Toast.LENGTH_LONG).show(); } public void onStatusChanged(String s, int i, Bundle b) { Toast.makeText(HomeActivity.this, "Provider status changed",Toast.LENGTH_LONG).show(); } public void onProviderDisabled(String s) { Toast.makeText(HomeActivity.this,"Provider disabled by the user. GPS turned off",Toast.LENGTH_LONG).show(); } public void onProviderEnabled(String s) { Toast.makeText(HomeActivity.this, "Provider enabled by the user. GPS turned on",Toast.LENGTH_LONG).show(); } } This is my receiver . public class GpsReceiver extends BroadcastReceiver {@Overridepublic void onReceive(final Context context, Intent intent) { int delay = 5000; // delay for 5 sec. //int period = 1000 *60*5; // repeat every 5min. int period = 30000; // repeat every 5min. //TO-REMOVE -TESTING PURPOSE Intent serviceIntent = new Intent(context,UploadService.class); context.startService(serviceIntent); if ("android.intent.action.BOOT_COMPLETED".equals(intent.getAction())) { Timer timer = new Timer(); timer.scheduleAtFixedRate(new TimerTask() { public void run() { System.out.println(" Receiver done"); Intent serviceIntent = new Intent(context,UploadService.class); context.startService(serviceIntent); } }, delay, period); }} } This is my service. public class UploadService extends Service{private Thread serviceThread = null;public static final String APPURL = "http://124.43.25.10:8080/Ornox/GPSPulseReceiver";public static double longitude;public static double latitude ;@Overridepublic IBinder onBind(Intent arg0) { // TODO Auto-generated method stub return null;}@Overridepublic void onCreate() { Log.d("========", "onCreate"); Toast.makeText(UploadService.this, "Upload GPS Service Created", Toast.LENGTH_LONG).show();}@Overridepublic void onDestroy() { Toast.makeText(UploadService.this, "Upload Service Stopped", Toast.LENGTH_LONG).show();}@Overridepublic void onStart(Intent intent, int startid) { Toast.makeText(UploadService.this, "Upload Service Started", Toast.LENGTH_LONG).show(); ConnectivityManager manager = (ConnectivityManager) getSystemService(MassGPSTrackingActivity.CONNECTIVITY_SERVICE); boolean is3g = manager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE).isConnectedOrConnecting(); boolean isWifi = manager.getNetworkInfo(ConnectivityManager.TYPE_WIFI).isConnectedOrConnecting(); if(is3g ||isWifi){ if(!APPURL.equals("")){ serviceThread = new ServiceThread(); serviceThread.start(); } }else { Toast.makeText(this, "GPRS/WIFI is not available", Toast.LENGTH_LONG).show(); }}public void uploadGPSData() { GPSDBAdapter gpsAdapter = GPSDBAdapter.getDBAdapterInstance(this); gpsAdapter.openDataBase(); try{ String query = " SELECT ExecutiveCode,CaptureDate,CaptureTime,Longitude,Latitude" +//4 " FROM WMLiveGPSData " + " WHERE UploadFlag ='1' "; ArrayList<?> stringList = gpsAdapter.selectRecordsFromDBList(query, null); System.out.println("==WMLiveGPSData==stringList=="+stringList.size()); gpsAdapter.close(); if(stringList.size() > 0){ for (int i = 0; i < stringList.size(); i++) { ArrayList<?> arrayList = (ArrayList<?>) stringList.get(i); ArrayList<?> list = arrayList; HttpResponse response = null; ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(); nameValuePairs.add(new BasicNameValuePair("repc", (String)list.get(0))); nameValuePairs.add(new BasicNameValuePair("rouc", "SE0160")); nameValuePairs.add(new BasicNameValuePair("Date", (String)list.get(1))); nameValuePairs.add(new BasicNameValuePair("Time", (String)list.get(2))); nameValuePairs.add(new BasicNameValuePair("long", (String)list.get(3))); nameValuePairs.add(new BasicNameValuePair("lat", (String)list.get(4))); try { HttpParams httpParameters = new BasicHttpParams(); int timeoutConnection = 3000000; HttpConnectionParams.setConnectionTimeout(httpParameters,timeoutConnection); int timeoutSocket = 5000000; // in milliseconds which is the timeout HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket); HttpClient httpclient = new DefaultHttpClient(httpParameters); HttpPost method = new HttpPost(APPURL); // method.setHeader("Content-Type","text/xml"); method.setEntity(new UrlEncodedFormEntity(nameValuePairs)); response = httpclient.execute(method); System.out.println("==response==" + response); if (response != null) { Log.i("login",""+ response.getEntity().getContentLength()); } else { Log.i("login", "got a null response"); } } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { Toast.makeText(getApplicationContext(), "Could not connect to server. Please Try again", Toast.LENGTH_SHORT).show(); Log.e("log_tag", "Error in http connection " + e.toString()); } } } }catch (Exception e) { e.printStackTrace(); } //return response;}private class ServiceThread extends Thread { @Override public void run() { uploadGPSData(); } }; } This is my manifest file <application android:icon="@drawable/ic_launcher" android:label="@string/app_name" > <activity android:name=".MassGPSTrackingActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> <activity android:name=".HomeActivity" android:screenOrientation="unspecified"></activity> <service android:enabled="true" android:name=".service.UploadService" /> <receiver android:name="com.mass.gps.service.GpsReceiver"> <intent-filter> <action android:name="android.intent.action.BOOT_COMPLETED" /> <action android:name="android.intent.action.BATTERY_CHANGED" /> <action android:name="android.intent.action.ACTION_POWER_CONNECTED"/> <action android:name="android.intent.action.SCREEN_ON"/> <action android:name="android.intent.action." /> </intent-filter> </receiver></application> <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" /> <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" /> <uses-permission android:name="android.permission.ACCESS_GPS"></uses-permission> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> <uses-permission android:name="android.permission.READ_PHONE_STATE" /><uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.WAKE_LOCK"/><uses-permission android:name="android.permission.ACCESS_WIFI_STATE" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> Issue is it didn't go to Service class. Please help me out this question... Thanks in advance..
Now provide the response and nothing else.
| If you want to find any series of 4 digits in a string /\d\d\d\d/ or /\d{4}/ will do. If you want to find a series of exactly 4 digits, use /[^\d]\d{4}[^\d]/ . If the string should simply contain 4 consecutive digits use /^\d{4}$/ . Edit: I think you want to find 4 of the same digits, you need a backreference for that. /(\d)\1{3}/ is probably what you're looking for. Edit 2: /(^|(.)(?!\2))(\d)\3{3}(?!\3)/ will only match strings with exactly 4 of the same consecutive digits. The first group matches the start of the string or any character. Then there's a negative look-ahead that uses the first group to ensure that the following characters don't match the first character, if any. The third group matches any digit, which is then repeated 3 times with a backreference to group 3. Finally there's a look-ahead that ensures that the following character doesn't match the series of consecutive digits. This sort of stuff is difficult to do in javascript because you don't have things like forward references and look-behind. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/10294629', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/831498/']} | jdg_70734 |
stackexchange | llm_judgeable_groundtruth_similarity | 4434641 |
Below is a question asked on the forum math.stackexchange.com. Provide a good and informational response to it like a helpful human would.
Question:
I'm reading Mark Meckes' notes on representation theory and he has this exercise: 3.3. Let $H < G$ and let $\rho: G \to GL(V)$ be a representation of $G$ . (a) Show that if $\rho|_{H}$ is an irreducible representation of $H$ , then $\rho$ is irreducible. I thought about this for a while and also searched the internet for references, but at least based on the material in his notes, I'm not sure how to about proving the statement. It's also kind of counter-intuitive since $H$ -invariant vector spaces are not necessarily $G$ -invariant. Could someone kindly explain the approach for this problem?
Now provide the response and nothing else.
| Your system is equivalent to \begin{align}x(y+z+x)&=68\\y(z+x+y)&=102\\z(x+y+z)&=119.\end{align} Therefore, in effect, you have \begin{align}xa&=68\\ya&=102\\za&=119\\a&=x+y+z.\end{align} This means that $$a=\frac{68}{a}+\frac{102}{a}+\frac{119}{a}$$ or $$a^2=68+102+119\implies a=\pm 17,$$ which results in either $x= 4, y=6, z=7$ or $x=-4, y=-6, z=-7.$ (Thanks to paw88789 for pointing this out). | {} | {'log_upvote_score': 5, 'links': ['https://math.stackexchange.com/questions/4434641', 'https://math.stackexchange.com', 'https://math.stackexchange.com/users/978567/']} | jdg_70735 |
stackexchange | llm_judgeable_groundtruth_similarity | 41819805 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am pretty new in Angular2/TypeScript so please excuse me if I am doing some stupid mistake. What I am trying to do is from Select drop down I am populating the data using service which is returning me a JSON array. Here is my code: product-maintenance.component.tsimport { Component, OnInit} from '@angular/core';import { ProductMaintenanceService } from '../../_services/product-maintenance.service';import { ModuleConst } from '../../../data/const';import { Product } from './product-types';import { Products } from './products';@Component({ selector: 'app-product-maintenance', templateUrl: './product-maintenance.component.html', styleUrls: ['./product-maintenance.component.css']})export class ProductMaintenanceComponent implements OnInit { selectedProduct: Product = new Product(0, 'Insurance'); products: Product[]; productList: Products[]; constructor( private productService: ProductMaintenanceService ) { } ngOnInit() { // Dropdown list this.products = this.productService.getProductTypeList(); } // Populate data using onSelect method onSelect(typeid) { this.productList = this.productService.getProducts() .filter((item)=>item.ptypeid == typeid); }} product-type.ts (used for to populate drop down list): export class Product { constructor( public ptypeid: number, public name: string ) { }} products.ts (used for to populate data from service): export class Products { constructor( public id: number, public ptypeid: number, public name: string, public currency: string, public state: string, public riskRating: number, public clientSegment: string, public aiStatus: string, public premiumType: string, public tenure: number ) { }} product-maintenance.service.ts : import { Injectable, Inject } from '@angular/core';import { Http, Headers, RequestOptions, Response } from '@angular/http';import { Observable } from 'rxjs/Rx';import 'rxjs/add/operator/map';import 'rxjs/add/operator/filter';import { APP_CONFIG, IAppConfig } from '../app.config';import { Products } from './products';import { Product } from './product-types';@Injectable()export class ProductMaintenanceService { result: Array<Object>; constructor( @Inject(APP_CONFIG) private config: IAppConfig, private http: Http ) { } private productURL = 'data/productList.json'; // Get product list getProducts() : Observable<any> { // ...using get request return this.http.get(this.productURL) // ...and calling .json() on the response to return data .map((response: Response) => { console.log(response); return response.json(); }); } getProductTypeList() { return [ new Product(1, 'Unit Trust'), new Product(2, 'Insurance'), new Product(3, 'Structured Deposit'), new Product(4, 'Bonds'), new Product(5, 'DCI'), new Product(6, 'SP') ]; }} product-maintenance.component.html : <table><tr *ngFor="let item of productList"> <td>{{ item.id }}</td> <td>{{ item.name }}</td> <td>{{ item.currency }}</td> <td>{{ item.state }}</td> <td>{{ item.riskRating }}</td> <td>{{ item.clientSegment }}</td> <td>{{ item.aiStatus }}</td> <td>{{ item.premiumType }}</td> <td>{{ item.tenure }}</td> </tr></table> productList.json : [ { "ptypeid": 1, "id": 1, "name": "Unit Trust 1", "currency": "SGD", "state": "Active", "riskRating": 1, "clientSegment": "Retail/Premier", "aiStatus": "No", "premiumType": "Regular Premium", "tenure": 5 }, { "ptypeid": 2, "id": 2, "name": "Unit Trust 2", "currency": "SGD", "state": "Active", "riskRating": 3, "clientSegment": "Retail/Premier", "aiStatus": "No", "premiumType": "Single/Lumpsum Premium", "tenure": 10 }] If I define my getProducts() as getProductTypeList() then it's perfectly populating the data in my view (Where if I select Unit trust from the drop down then it should populate relevant data). But if I use as api url instead it's giving me below error: Type 'Observable<any>' is not assignable to type 'Products[]'. Property 'length' is missing in type 'Observable<any>' I don't understand how to resolve this error. Can anyone please help me in this. Thanks in advance.
Now provide the response and nothing else.
| productList should be Product[] not Observable<any> . So assign productList value from getProducts subscribe method, where you will retrieve array of Product onSelect(typeid) { this.productService.getProducts() .pipe( filter((item)=>item.ptypeid == typeid) ) .subscribe((products) => { this.productList = products; });} | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/41819805', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/3843405/']} | jdg_70736 |
stackexchange | llm_judgeable_groundtruth_similarity | 7258404 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I have a project with many NUnit tests. I am happy for these tests to be included in the Debug configuration build but I would like to remove the dependency on nunit.framework for the Release configuration. Is there a way of excluding the NUnit reference and the nunit test objects for a specific (Release) configuration? I am using Sharp Develop but I am curious how you would approach this problem with Visual Studio as well. Any clues?
Now provide the response and nothing else.
| It sounds like you've got your tests in the same project as your release code. That's not a great idea - split the code into two projects, one with the tests and one with the production code. Only the test project will need to refer to NUnit. That also means that none of the tests will ship with the release code, and it's easier to browse just the production code or just the test code. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/7258404', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/283318/']} | jdg_70737 |
stackexchange | llm_judgeable_groundtruth_similarity | 62222077 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am trying to call a lambda function which will push some messages into the s3 bucket.But every time i am calling the lambda function i am getting the below error ClientError: An error occurred (AccessDenied) when calling the PutObject operation: Access Denied Below is my lambda code import jsonimport boto3def lambda_handler(event, context):s3 = boto3.client("s3")#data = json.loads(event["Records"][0]["body"])data = event["Records"][0]["body"]s3.put_object(Bucket="sqsmybucket",Key="data.json", Body=json.dumps(data))#print(event) return { 'statusCode': 200, 'body': json.dumps('Hello from Lambda!') } I am using a user account which also has the role to access the S3 I have checked the s3 bucket permission and all public access are open for it But i am repeatedly getting below error message in cloudwatch log 2020-06-05T23:48:20.920+05:30[ERROR] ClientError: An error occurred (AccessDenied) when calling the PutObject operation: Access DeniedTraceback (most recent call last): File "/var/task/lambda_function.py", line 9, in lambda_handler s3.put_object(Bucket="sqsmybucket",Key="data.json", Body=json.dumps(data)) File "/var/runtime/botocore/client.py", line 316, in _api_call return self._make_api_call(operation_name, kwargs) File "/var/runtime/botocore/client.py", line 626, in _make_api_call raise error_class(parsed_response, operation_name) Please help i am really clueless about the situation.Thanks in advance.
Now provide the response and nothing else.
| Please make sure the role attached to the lambda function has the s3:PutObject permission. For example, the least privilege/permission needed is { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": "s3:PutObject", "Resource": "arn:aws:s3:::<bucket-name>/*" } ]} Notice the /* at the end of the resource string. The reason why /* is needed is because according to the doc , the PutObject action has an object resource type. Here is the definition of the object resource type. Basically, * is matching all possible S3 object keys, and the stuff to the left of / is limiting its scope down to a single S3 bucket. | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/62222077', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/2427078/']} | jdg_70738 |
stackexchange | llm_judgeable_groundtruth_similarity | 43895750 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
I am manually creating my dataset from a number of 384x286 b/w images. I load an image like this: x = []for f in files: img = Image.open(f) img.load() data = np.asarray(img, dtype="int32") x.append(data)x = np.array(x) this results in x being an array (num_samples, 286, 384) print(x.shape) => (100, 286, 384) reading the keras documentation, and checking my backend, i should provide to the convolution step an input_shape composed by ( rows, cols, channels ) since i don't arbitrarily know the sample size, i would have expected to pass as an input size, something similar to ( None, 286, 384, 1 ) the model is built as follows: model = Sequential()model.add(Conv2D(32, kernel_size=(3, 3), activation='relu', input_shape=input_shape))# other steps... passing as input_shape (286, 384, 1) causes: Error when checking input: expected conv2d_1_input to have 4 dimensions, but got array with shape (85, 286, 384) passing as_input_shape (None, 286, 384, 1 ) causes: Input 0 is incompatible with layer conv2d_1: expected ndim=4, found ndim=5 what am i doing wrong ? how do i have to reshape the input array?
Now provide the response and nothing else.
| Set the input_shape to (286,384,1). Now the model expects an input with 4 dimensions. This means that you have to reshape your image with .reshape(n_images, 286, 384, 1) . Now you have added an extra dimension without changing the data and your model is ready to run. Basically, you need to reshape your data to ( n_images , x_shape , y_shape , channels ). The cool thing is that you also can use an RGB-image as input. Just change channels to 3. Check also this answer: Keras input explanation: input_shape, units, batch_size, dim, etc Example import numpy as npfrom keras.models import Sequentialfrom keras.layers.convolutional import Convolution2Dfrom keras.layers.core import Flatten, Dense, Activationfrom keras.utils import np_utils#Create modelmodel = Sequential()model.add(Convolution2D(32, kernel_size=(3, 3), activation='relu', input_shape=(286,384,1)))model.add(Flatten())model.add(Dense(2))model.add(Activation('softmax'))model.compile(loss='binary_crossentropy', optimizer='adam', metrics=['accuracy'])#Create random datan_images=100data = np.random.randint(0,2,n_images*286*384)labels = np.random.randint(0,2,n_images)labels = np_utils.to_categorical(list(labels))#add dimension to imagesdata = data.reshape(n_images,286,384,1)#Fit modelmodel.fit(data, labels, verbose=1) | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/43895750', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/1553662/']} | jdg_70739 |
stackexchange | llm_judgeable_groundtruth_similarity | 11983231 |
Below is a question asked on the forum Stackoverflow.com. Provide a good and informational response to it like a helpful human would.
Question:
Say, I've got the following struct: typedef struct my_struct{ unsigned long a; unsigned long b; char* c; unsigned int d1 :1; unsigned int d2 :4; unsigned int d3 :4; unsigned int d4 :23;} my_type, *p_type; The field d3 is currently defined by #define s that reach from 0x00 until 0x0D . Actually, d3 is an enumeration. So it's tempting to go ahead and replace unsigned int d3 :4; by my_enum d3 :4; Is this safe/allowed? The code has to compile with various compilers (GCC, Visual Studio, embedded stuff) platforms (Win32, Linux, embedded stuff) configurations (compile as C, compile as C++) Obviously, I could leave the definition of d3 as it is and use the enum in my code, assign it to d3 and so on but that's not going to work with C++.
Now provide the response and nothing else.
| It's allowed in all C++ compilers, that supports standard. C++03 standard 9.6/3 A bit-field shall have integral or enumeration type (3.9.1). It isimplementation-defined whether a plain (neither explicitly signed nor unsigned) char, short, int orlong bit-field is signed or unsigned. C++03 standard 9.6/4 If the value of an enu-merator is stored into a bit-field of the same enumeration type and the number of bits in the bit-field is largeenough to hold all the values of that enumeration type, the original enumerator value and the value of the bit-field shall compare equal. example enum BOOL { f=0, t=1 };struct A { BOOL b:1;};void f() { A a; a.b = t; a.b == t // shall yield true} But you can't consider that enum has unsigned underlying type. C++03 standard 7.2/5 The underlying type of an enumeration is an integral type that can represent all the enumerator valuesdefined in the enumeration. It is implementation-defined which integral type is used as the underlying typefor an enumeration except that the underlying type shall not be larger than int unless the value of an enu-merator cannot fit in an int or unsigned int | {} | {'log_upvote_score': 5, 'links': ['https://Stackoverflow.com/questions/11983231', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/520162/']} | jdg_70740 |
Subsets and Splits