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Lets say I want to download the 'Full GNOME Desktop Environment, with extra components' in the image below. What is the name of the package? is it 'gnome' or 'Full GNOME Desktop Environment, with extra components' or ...? | Hello I want to remove software (for example transmission) using Terminal. How can i find the package name for the software ? |
I recently (yesterday) followed and noticed that I'm not in the list of followers: and the followers count is 19 which is exactly the number of user in that list (without me). Am I missing something? (cached?) | I know of one person who is following my proposal who doesn't show up on the proposal webpage. My proposal is for quantitative finance: . It shows 19 people following the proposal (on the side of the page), and the total listed at the top of the page is 19 followers. Yet one user is not listed: . This makes me wonder if other followers are also not being counted? |
when I updating with sudo apt-get update , I got this: N: Ignoring file '20auto-upgrades.ucf-dist' in directory '/etc/apt/apt.conf.d/' as it has an invalid filename extension W: The repository 'http://ppa.launchpad.net/lucid-bleed/ppa/ubuntu xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: Failed to fetch http://ppa.launchpad.net/lucid-bleed/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found E: Some index files failed to download. They have been ignored, or old ones used instead. my question is: What is this error and how do I understand it. What should I do to solve this problems. | PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown: W: Failed to fetch http://ppa.launchpad.net/ 404 Not Found How do I fix these errors? |
I am attempting to add a value to a list at a specific index, which according to everything I've read, should be do-able with List's Insert() method. Except I'm getting the exception "Index must be within the bounds of the List. Parameter name: index` Here is my complete sample code. class Program { static void Main(string[] args) { MyList myList = new MyList(); } } class MyList : List<int> { public MyList() { this.Capacity = 2; this.Insert(1, 0); } } Is the only option to change to a nullable list type and call .Add(null) for each index and not use Insert()? | .NET offers a generic list container whose performance is almost identical (see Performance of Arrays vs. Lists question). However they are quite different in initialization. Arrays are very easy to initialize with a default value, and by definition they already have certain size: string[] Ar = new string[10]; Which allows one to safely assign random items, say: Ar[5]="hello"; with list things are more tricky. I can see two ways of doing the same initialization, neither of which is what you would call elegant: List<string> L = new List<string>(10); for (int i=0;i<10;i++) L.Add(null); or string[] Ar = new string[10]; List<string> L = new List<string>(Ar); What would be a cleaner way? EDIT: The answers so far refer to capacity, which is something else than pre-populating a list. For example, on a list just created with a capacity of 10, one cannot do L[2]="somevalue" EDIT 2: People wonder why I want to use lists this way, as it is not the way they are intended to be used. I can see two reasons: One could quite convincingly argue that lists are the "next generation" arrays, adding flexibility with almost no penalty. Therefore one should use them by default. I'm pointing out they might not be as easy to initialize. What I'm currently writing is a base class offering default functionality as part of a bigger framework. In the default functionality I offer, the size of the List is known in advanced and therefore I could have used an array. However, I want to offer any base class the chance to dynamically extend it and therefore I opt for a list. |
I am dealing with the following exercise A set $\mathcal M$ in a normed linear space $\mathcal R$ is said to be convex if $\mathcal M$ contains all elements of the form $\alpha x + \beta y$, where $\alpha, \beta \geq 0$, $\alpha+\beta=1$, provided that $\mathcal M$ contains x and y. Prove that the set of all elements $x \in \mathcal R$ satisfying the inequality $\|x-x_0 \| \leq c$, where $x_0$ is a fixed element of $\mathcal R$ and $c > 0$, is convex. Assume $\|x-x_0 \|\leq c$, and $\|y-x_0 \| \leq c$, we have to proof that $$\| \alpha x + (1-\alpha) y - x_0 \| \leq c.$$ By the triangular inequality, $$\begin{align*}\| \alpha x + (1-\alpha) y - x_0 \| & \leq \| \alpha x \| + \|(1-\alpha) y - x_0 \| \\ & \leq \| \alpha x \| + \|(1-\alpha) y \| +\|- x_0 \| \\ & \leq |\alpha| \| x \| + |(1-\alpha)| \| y \| +\| x_0 \| \\ & = c.\end{align*}$$ Is it enough for proof the theorem? If not, what path should I take? | If $(X,\|\cdot\|)$ is a normed linear space, then how to show any ball $B(x,r)$ is convex? I know that if $x,y\in A\subset V$ then $[x,y]\subset A$, where $A$ is a convex subset of vector space $V$ and $[x,y]=\{(1-t)x+ty\mid 0\leq t \leq 1\}$. Please give me some hint. I tried the following: Claim. $[a,b] \subset B(x,r)$ Let $a,b \in B(x,r).$ Then I get $\|x-a\|<r$ and $\|x-b\|<r$. Is it right? |
Are there arbitary larger numbers of the form $a^b$ with positive integers $a,b>1$ and $a\ne 0\mod 10$ NOT containing all digits ? Here : is either a very similar or the same question, but the question is so old that I decided to restate it. My current best example : The number $1955^{39}$ has $129$ digits, but does not contain the digit $1$. If we assume that the digits are uniformly distributed in $[0,9]$ and considering the growth of the non-trivial powers, can we expect that we have enough chances to get , lets say , a $1000$-digit example ? In other words, are there enough non-trivial powers with a given decimal-expansion-length, that we can expect that the answer to the question is yes ? | Let $m>1$ be a natural number with $m \not\equiv 0 \pmod{10}$ Consider the powers $m^n$ , for which there is at least one digit not occurring in the decimal representation. Is there a largest $n$ with the desired property for any $m$? If so, define $n(m)$ to be this number. Examples : $$m=2 \rightarrow 2^{168} = 374144419156711147060143317175368453031918731001856$$ does not contain the digit $2$. All the powers above up to $2^{10000}$ conatin all the digits, so $2^{168}$ seems to be the biggest power with the desired property. $$m=3 \rightarrow 3^{106} = 375710212613636260325580163599137907799836383538729$$ does not contain the digit $4$. All the powers above up to $3^{10000}$ contain all the digits, so $3^{106}$ seems to be the biggest power with the desired property. So, probably $n(2)=168$ and $n(3)=106$ hold. Is $n(m)$ defined for any $m$, and if yes, can reasonably sharp bounds be given? |
I am new to PowerShell and I am stuck with a script to parse CSV document to identify if the emails are in proper format or not. My script does execute but instead of filtering records with invalid email it exports all records with the selected columns. Please suggest as what I am missing. $sourceFile = "d:\rvcc.csv" $targetFile = "d:\LMI-Invalid_Users_{0:yyyyMMMdd-HHmm}.csv" -f (Get-Date) $validemailDomain1 = "^[a-z]+\.[a-z][email protected]$" $validemailDomain2 = "^[a-z][email protected]$" $validemailDomain3 = "^[a-z0-9][email protected]$" $blankemail="" Import-CSV $sourceFile | % { # The big blue bar: Or Verbose text: Write-Verbose "Checking: $($_.EmailAddress)" Write-Progress -Activity "Checking user" -Status $_.EmailAddress If ($_.EmailAddress -NotMatch $validemailDomain1 -or $_.EmailAddress -NotMatch $validemailDomain2 -or $_.EmailAddress -NotMatch $validemailDomain3 -or $_.EmailAddress -NotMatch $blankemail) { $_ | Select-Object EmailAddress, FirstName, LastName, UserType, School_Id } } | Export-CSV $targetFile -NoTypeInformation | Over the years I have slowly developed a that validates MOST email addresses correctly, assuming they don't use an IP address as the server part. I use it in several PHP programs, and it works most of the time. However, from time to time I get contacted by someone that is having trouble with a site that uses it, and I end up having to make some adjustment (most recently I realized that I wasn't allowing 4-character TLDs). What is the best regular expression you have or have seen for validating emails? I've seen several solutions that use functions that use several shorter expressions, but I'd rather have one long complex expression in a simple function instead of several short expression in a more complex function. |
I have and Excel file that I converted to a CSV file. Apparently there are two kinds of spaces in this file, the regular space and a non-breaking space (my assumption). When saving the data to the database the non-breaking space gets saved as a black diamond with a question mark (�). I've been reading around as this probably has solutions already but when I try them, nothing is happening. Using the mb_substr approach: $name = !empty($data[0]) ? mb_substr($data[0], 0, mb_strlen($data[0]), "UTF-8") : null; Using the str_replace approach: $name = !empty($data[0]) ? str_replace("&nbsp;", " ", $data[0]) : null; I've been pulling my hair out with this one for a couple of hours now so if anyone could help me out, I highly appreciate it. EDIT I'm using Oracle for the database and here are the Character Sets defined: NLS_CHARACTERSET = AL32UTF8 NLS_NCHAR_CHARACTERSET = AL16UTF16 Here's a sample data: , W.R., The space before W is the character that gets transformed into the question mark. | I'm writing a php program that pulls from a database source. Some of the varchars have quotes that are displaying as black diamonds with a question mark in them (�, , I assume from Microsoft Word text). How can I use php to strip these characters out? |
I am trying to learn discrete mathematics on my own and have been reading Rosen's discrete math textbook, there is one step in his proof that I do not understand. Where $<2*k!$ becomes $(K + 1)K!$ he states that $2 < k + 1$ but how is he determining that? I have attached an image of the proof for viewers to see exactly, it is the second last line of the inequalities. | Im trying to solve the following question In the second step where do they get $k!=2^k-1?$ |
I'm curious if it's possible to install Ubuntu on a blank HD over the network. This is an HP windows home/media server (hp ex490), with no CD/DVD rom. The server doesn't seem to respond to a USB monitor, keyboard or mouse. I feel like there's information out there already on this, but I come up empty on Google. | I would like to install Ubuntu for almost 120 users. But it's very difficult in using USB and drives. Any suggestions? |
I would like to be able to preview and capture photos from two cameras simultaneously, and download them to my computer. Being able to keep track of which photos were from which camera is also a must. I haven't bought the cameras yet, and I do not have any requirements as to which cameras are supported (it seems the packages above only support Canons). On the other hand I need a digital camera with 1024*1280 pixel resolution. I also want to control the capturing step and frequency with software on my computer. My requirement is about 20 pictures per minute. What's the best model camera and software for this purpose? And how I can connect these camera to my computer? | I have 10 Canon 5DmkII cameras which I want to fire simultaneously... How can I accomplish this task repeatedly and reliably? NOTE: Although I mention 10 cameras, it will be a 'super bonus' if the solution is scalable to n cameras... |
At the end of season 2 of Stardust Crusaders, the blood from Dio's corpse was transfused back to Joseph Joestar. However, as seen before in the series, the contact of Dio's blood with a corpse makes the corpse a Vampire. It was also explicitly stated that Dio's body was still not "dead". Then why did this not happen to Joseph? | At the end of JoJo season 3: episode 48: Dio Brando killed Joseph Joestar using 'The World'. Later on, Dio drained his blood entirely and left Joseph Joestar as a husk. However, Jotaro was able to revive Joseph by transferring blood from Dio's dead body into his Grand Dad. () What I'm trying to understand though is why Joseph did not turn into an undead vampire. Because I remember the episode before that, Dio had previously used his blood to turn into a vampire (the one with the "self-eating" Stand). |
I can't understand when I need one and two backward slashes \. First, see an example: const rxHttps = new RegExp("\/"); console.log(rxHttps.test("/")); // true const rxQuestion = new RegExp("\\?"); console.log(rxQuestion.test("?")); // true const rxAnotherQuestion = new RegExp("\?"); // Uncaught SyntaxError: Invalid regular expression: /?/: Nothing to repeat In the above example, to use a character /, it needs just one \. However, ? needs two \, or SyntaxError occurs. This is really confusing. I can't make heads or tails of it. Why are they different? Am I misunderstanding? | I am tired of always trying to guess, if I should escape special characters like '()[]{}|' etc. when using many implementations of regexps. It is different with, for example, Python, sed, grep, awk, Perl, rename, Apache, find and so on. Is there any rule set which tells when I should, and when I should not, escape special characters? Does it depend on the regexp type, like PCRE, POSIX or extended regexps? |
I am working with a $pq$ group. Where $p=7,q=11$. I have so far managed to prove that such a group is cyclic and hence abelian. My question asks what is this group isomorphic to and I don't really know. I do remember learning that we can classify all finite abelian groups into direct products of cyclic groups but I don't remember the specifics sorry. As a guess I would think maybe our group of order $77$ is either isomorphic to $\mathbb{Z}_{77}$ or maybe $\mathbb{Z}_{7} \times \mathbb{Z}_{11}$ but I really don't know how to show this? | I don't know about the Sylow Theorems. But I have been wondering about a proof of the fact that a group or order $pq$ where $p$ and $q$ are distinct primes must be cyclic. I can't quite work out the details, but here is the general idea. I would like help with filling in details. I assume that it is already known that $G$ has subgroup(s) of order $p$ and subgroup(s) of order $q$. If $G$ is a group of order $pq$ ($p\neq q$), then I know that $G$ has a subgroup $H$ of order $p$ and a subgroup $K$ of order $q$. Then $H\simeq \mathbb{Z}_p$ and $K\simeq \mathbb{Z}_q$. But then $H\oplus K \simeq \mathbb{Z}_{pq}$, so I would think that $H\oplus K \simeq G$. I guess one could do an internal direct product instead of an external direct product, but I don't know that $H$ and $K$ are normal subgroups. I am asking for help completing this argument. Edit: I see from the comments below that I might need to assume that the smaller prime does not divide the larger prime minus $1$. Or maybe it is enough to assume that the primes are greater than or equal to $3$ (Still distinct). |
I've been using Xenial 16.04 and I'm thinking of installing 14.04 alongside the existing one so that I can do dual boot. Is this possible? And if so, how can I do it? I'm afraid that I might blow off my Xenial because I've never tried dual booting before.. I would really appreciate your help. | I have a dilemma and I don't know what to do. Currently I have Ubuntu 14.04 64 bit installed along side Windows 7 64 bit and everything works wonderfully. I recently started a course about Assembly on Linux and the professor recommended downloading Ubuntu 12.04 32 bit. I downloaded the iso file and loaded it on to a USB. When I first installed Ubuntu 14.04, it gave me the following 3 options: 1) install Ubuntu alongside Windows 2) delete Window and install Ubuntu 3) Something Else I choose the first option. However, when I attempted to install Ubuntu 12.04 32bit along side Ubuntu 14.04 64 Bit and Windows 64 bit, the first option was gone. Instead I was given the following 3 options: 1) Delete 14.04 and install 12.04 in its place 2) Delete both 14.04 and Windows 7 and install 12.04 as replacement 3) Something Else My question is this: is it advisable to install Ubuntu 12.04 32 bit along side Ubuntu 14.04 64 bit and Windows 7 as the Ubuntu Installer no longer gives me this option? Should I just go ahead and replace 14.04 with 12.04 for the duration of time that I would need it. I don't want to delete 14.04 but I will if need be. I also like the current Dual boot option Ubuntu has put in place so if making a 4th partition through way of "Something Else" would delete that, I would much rather delete 14.04 to make room for 12.04. Again my preference would be to have Ubuntu 12.04 32 bit appear alongside Ubuntu 14.04 64 bit and Windows 7 when I boot my computer, but short of that, I would settle for Ubuntu 12.04 32 bit appearing alongside Windows 7 for the time being. I look forward to your advice. |
Error mounting /dev/sda3 at /media/dany/Data: Command-line `mount -t "ntfs" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000,dmask=0077,fmask=0177" "/dev/sda3" "/media/dany/Data"' exited with non-zero exit status 14: The disk contains an unclean file system (0, 0). Metadata kept in Windows cache, refused to mount. Failed to mount '/dev/sda3': Operation not permitted The NTFS partition is in an unsafe state. Please resume and shutdown Windows fully (no hibernation or fast restarting), or mount the volume read-only with the 'ro' mount option. | Whenever I boot Ubuntu, I get a message that it cannot mount my windows partition, and I can choose to either wait, skip or manually mount. When I try to enter my Windows partition through Nautilus I get a message saying that this partition is hibernated and that I need to enter the file system and properly close it, something I have done with no problem so I don't know why this happens. Here's my partition table, if any more data is needed please let me know. Device Boot Start End Blocks Id System /dev/sda1 2048 20000767 9999360 83 Linux /dev/sda2 20002814 478001151 228999169 5 Extended /dev/sda3 * 478001152 622532607 72265728 7 HPFS/NTFS/exFAT /dev/sda4 622532608 625141759 1304576 82 Linux swap / Solaris /dev/sda5 20002816 478001151 228999168 83 Linux |
The statement $$\forall x \in \mathcal{R} \exists n \in \mathcal{N} (n>x)$$ Is true, but $$\exists n \in \mathcal{N} \forall x \in \mathcal{R} (n>x)$$ Is false. Why does reversing the order of the quantifiers cause the first statement to become false? | I'm working with the universal and the existential quantifiers and I was wondering is there an order of operations that applies to them? What is the difference between $(\forall x)P(x)(\exists x)Q(x)$ And $(\exists x)Q(x)(\forall x)P(x)$ Lets say we have this relationship (a) $[(\forall x)P(x) \vee (\exists x)Q(x)] \implies (\forall x)[P(x) \vee Q(x) ]$ |
Here's the scenario. I have a HP laptop in which I installed Windows 10 Technical Preview a few months ago. Now, when I tried to turn it ON, it gave me an error "Your PC/device needs to be repaired", error 0x0000428. What I exactly want to do is, I want to format my entire hard drive so that I can reinstall Windows 7 in it but I don't know how to format it as I am unable to do anything with that error code in my laptop. I don't have disc for Windows 10 Technical Preview. | Is there a Disc Formatter out there that i can boot into using a CD and format my Harddrive. I know i could use fedora CD but i was wondering if there is one out there that will make sure the data is actually gone and not just there links. |
Let's say I have two Minecraft worlds and 20 mods. Can I make not enough items work with both the worlds but the other mods only work in the other world? | I have lots of mods installed on my Minecraft client. How can I make certain mods only work in certain worlds? For example, how can I make the train mod work only for one of my worlds not the others and have BuildCraft work for all my worlds except the one with the train mod? |
I'm seeing a spacing issue under Achievements on iOS mobile Safari: Is this a know issue? Device: iPhone 6 OS Version: Version 9.1 (Build 13B143) | There is some weird spacing on the mobile web site: Additionally, the main font color has changed from black to yellow: Can this be fixed please? |
My code structure: /foo __init__.py bar.py init.py import bar eval("import bar") It raises SyntaxError when execute the second line. >>> import foo Traceback (most recent call last): File "<stdin>", line 1, in <module> File "foo/__init__.py", line 2, in <module> eval('import bar') File "<string>", line 1 import bar ^ SyntaxError: invalid syntax I am confused because I would expect behaviors of these codes should be the same. | I'm writing a Python application that takes as a command as an argument, for example: $ python myapp.py command1 I want the application to be extensible, that is, to be able to add new modules that implement new commands without having to change the main application source. The tree looks something like: myapp/ __init__.py commands/ __init__.py command1.py command2.py foo.py bar.py So I want the application to find the available command modules at runtime and execute the appropriate one. Python defines an __import__ function, which takes a string for a module name: __import__(name, globals=None, locals=None, fromlist=(), level=0) The function imports the module name, potentially using the given globals and locals to determine how to interpret the name in a package context. The fromlist gives the names of objects or submodules that should be imported from the module given by name. Source: So currently I have something like: command = sys.argv[1] try: command_module = __import__("myapp.commands.%s" % command, fromlist=["myapp.commands"]) except ImportError: # Display error message command_module.run() This works just fine, I'm just wondering if there is possibly a more idiomatic way to accomplish what we are doing with this code. Note that I specifically don't want to get in to using eggs or extension points. This is not an open-source project and I don't expect there to be "plugins". The point is to simplify the main application code and remove the need to modify it each time a new command module is added. |
I noticed that my path environment variable had the path for my home's binaries $HOME/bin. I did not add $HOME/bin directory to my path environment variable so how did $HOME/bin get added to the path? RE - : This question is specific to the environment variable "PATH" and is further specific to how does a specific value, i.e. $HOME/bin, get appended to the environment variable. The "possible duplicate": does NOT mention the environment variable PATH anywhere in the question or answer does NOT mention anything about $HOME/bin anywhere in the question or answer | I have a Linux instance that I set up some time ago. When I fire it up and log in as root there are some environment variables that I set up but I can't remember or find where they came from. I've checked ~/.bash_profile, /etc/.bash_rc, and all the startup scripts. I've run find and grep to no avail. I feel like I must be forgetting to look in some place obvious. Is there a trick for figuring this out? |
I have a model from Source Filmmaker that has a bunch of different textures. It's all imported and ready to be textured using Blender nodes, but since there are so many objects (over 40) in this particular model, I figure it would be a waste of time to manually reshade/texture every single material which could take several hours. Instead, I could just write a simple script that could read the texture VMT files (from SFM) which define what each texture file is for (diffuse, bumpmap, etc.) in batch and create all the Blender shaders nodes automagically once the .blend file is there. The snag is .blend is a binary file, and I can't read it or edit it in a text editor. Is there any way at all to create Blender nodes programmatically (i.e. not inside the Blender GUI but perhaps importing other things or using addons?) | How can I define the different properties of an Cycles/Eevee material? Such things as glossy, glass, diffuse, RGB-color, emissive via python scripting? |
I am very new to Number Theory, I understood the basic concepts and theorems but what I am struggling at is that I am not able to apply them on questions, and basically I am not able to process the problem in 'number theory' theorems rather I am thinking from an absolute manner. I have solved around 15-20 divisibility problems of Number Theory and I still have no idea how you deal with congruences in a real problem, for example: Prove that for positive integer $ n$ we have $169| 3^{3n+3}-26n-27$. My approach to this problem was by simplifying the expression as much as I can but it involved congruences, which didn't even strike me. Even when I am reading congruence questions' answers, I am not able to simply understand Now I have a number of questions: first, does it take time to develop that 'intuition' while solving problems? second, can elementary number theory be mastered through sheer practice? third, is there a good resource to study and practice congruences? | $ 169$ | $3^{3n+3}-26n-27$ ? Fulfilled for $n=0$. Induction to $n+1$: An integer $x$ exists so that $ 169x= 3^{3n+6}-26n-27-26$ $ 169x= 27*3^{3n+3}-26n-27-26$ $ 169x= 26*3^{3n+3}+3^{3n+3}-26n-27-26$ An integer $m$ exists so that $ 169x= 26*3^{3n+3}+169m-26$ ($ 13x= 2*(3^{3n+3}-1)+13m$) Now I'm stuck although it looks simple. Thanks for any input in advance. |
In java script there is an alternative to if statement i mean like ternary operator : (boolean expression )? option 1: option 2, it is elegant compact and sometimes less confusing. I have searched a lot to find an alternative for 'if' statement in python but i couldn't find anything. Is there any way to trick python so we can avoid if statement ? | If Python does not have a ternary conditional operator, is it possible to simulate one using other language constructs? |
On my computer I have a typical SATA SSD (with my current Windows 10 installation) and and another separate M.2 SSD. I have more than enough space on my normal SSD and would like to install KUbuntu on my M.2 SSD. As I read through questions about dual booting, I see warnings about things like UEFI, Secure Boot, and Fast Startup and wonder if they apply to me since most of the time it seems as if they are all talking about dual booting from the same drive. I have the installer flashed to a USB drive right now but I would like to know if I should be worried about anything such as corrupting my Windows installation. I would like to know if I can keep fast startup on, if I have to change anything with UEFI or secure boot, and if I have to unplug anything like the people on this discussion are talking about; Also feel free to give me some simple partition layouts geared towards programming for my KUbuntu installation :) | I have recently got an Alienware M17x R4 and since it has two hard drive bays I was thinking of putting my hard drive from my old laptop and installing Ubuntu on it without making any changes to the drive that has Windows on it. Also if possible to add a entry to the Windows boot loader to boot Ubuntu instead of using GRUB. |
This code was taken from another post at where it was pointed out that there is an SQL injection vulnerability. What about this code is vulnerable, how could it be exploited, and how can it be made safe? <?php include("config.php"); function getAllVotes($id) { $votes = array(); $q = "SELECT * FROM entries WHERE id = $id"; $r = mysql_query($q); if(mysql_num_rows($r)==1)//id found in the table { $row = mysql_fetch_assoc($r); $votes[0] = $row['votes_up']; $votes[1] = $row['votes_down']; } return $votes; } function getEffectiveVotes($id) { $votes = getAllVotes($id); $effectiveVote = $votes[0] - $votes[1]; //ERROR THROWN HERE return $effectiveVote; } $id = $_POST['id']; $action = $_POST['action']; //get the current votes $cur_votes = getAllVotes($id); //ok, now update the votes if($action=='vote_up') //voting up { $votes_up = $cur_votes[0]+1; //AND ERROR THROWN HERE $q = "UPDATE threads SET votes_up = $votes_up WHERE id = $id"; } elseif($action=='vote_down') { $votes_down = $cur_votes[1]+1; $q = "UPDATE threads SET votes_down = $votes_down WHERE id = $id"; } $r = mysql_query($q); if($r) { $effectiveVote = getEffectiveVotes($id); echo $effectiveVote." votes"; } elseif(!$r) //voting failed { echo "Failed!"; } ?> | If user input is inserted without modification into an SQL query, then the application becomes vulnerable to , like in the following example: $unsafe_variable = $_POST['user_input']; mysql_query("INSERT INTO `table` (`column`) VALUES ('$unsafe_variable')"); That's because the user can input something like value'); DROP TABLE table;--, and the query becomes: INSERT INTO `table` (`column`) VALUES('value'); DROP TABLE table;--') What can be done to prevent this from happening? |
So, I have field called name on my custom field and I am writing a before trigger insert trigger to copy the name of the other lookup field into the name field which is a standard required field and looks like I cannot remove the required on the field. Now, my trigger copies the name of the other field into the name field only if I write something before saving. If I don't fill the name and try to save the record I get the error 'The following field must be completed : name' . How do I solve this because I cannot ask users to fill some rubbish as the name and tell them not to worry cause once they save the field the contents of the other field get copied ? Which is not bright I suppose. if(Trigger.isBefore){ //Process before insert that is to copy the name of the Template Id into the name of the checklist object set<Id>CheckListTemplateId = new set<Id>(); for(CheckList__c c : Trigger.new){ if(c.TemplateId__c != null){ CheckListTemplateId.add(c.TemplateId__c); } } System.debug('The set value is :' + CheckListTemplateId); if(!CheckListTemplateId.isEmpty()){ Map<Id,CheckListTemplate__c> checkListTemplateObj = new Map<Id,CheckListTemplate__c>([Select Id, Name From CheckListTemplate__c Where Id IN: CheckListTemplateId]); for(CheckList__c c : Trigger.New){ if(checkListTemplateObj.get(c.TemplateId__c).name != null){ // Copy the value of Template name from CheckListTemplate__c into name in CheckList__c c.Name = checkListTemplateObj.get(c.TemplateId__c).name; } } } } | I am trying to copy the value of user selected Status value into the standard salesforce required Company field. Now, when I try to save the record on the object since I am not entering any value in the Company field, the record is not being saved. How do I solve this kind of issue? Any leads appreciated trigger CopyStatusToTitle on Lead (before insert, after insert) { List<Lead> leadList = new List<Lead>(); if(Trigger.isInsert){ if(Trigger.isBefore){ //process before insert for(Lead l : trigger.New){ l.Company = l.Status; } }else if(Trigger.isAfter){ //process after insert } } } |
I found a way to prove this using Chebychev's theorem, are there ways to solve it without relying on this? | If $n>1$ is an integer, then $\sum \limits_{k=1}^n \frac1k$ is not an integer. If you know , then you know there must be a prime $p$ between $n/2$ and $n$, so $\frac 1p$ appears in the sum, but $\frac{1}{2p}$ does not. Aside from $\frac 1p$, every other term $\frac 1k$ has $k$ divisible only by primes smaller than $p$. We can combine all those terms to get $\sum_{k=1}^n\frac 1k = \frac 1p + \frac ab$, where $b$ is not divisible by $p$. If this were an integer, then (multiplying by $b$) $\frac bp +a$ would also be an integer, which it isn't since $b$ isn't divisible by $p$. Does anybody know an elementary proof of this which doesn't rely on Bertrand's Postulate? For a while, I was convinced I'd seen one, but now I'm starting to suspect whatever argument I saw was wrong. |
There’s something wrong with my Windows boot. But before I reinstall Windows 10, I need to backup my Minecraft saves with Linux. So I use Linux live USB mount into Windows system disk, but I can’t find my .minecraft folder! The folder should be in Local/Users/Andare/AppData/Roaming. There’re many other folders. But I didn’t find .minecraft. And I tried to search .minecraft, but I got no results! Could the folder be hidden? | I wanted to add classpath to my JDK. While searching a way to do it I noticed everyone open .profile file using terminal. But when I want to open and edit it with a text editor I couldn't see that file in Home folder. Can someone tell me why is this. And also if possible how can I access .profile in home folder the GUI way. |
How to go about consolidating three stack exchange accounts? | I accidentally posted a question without being logged in. Is there a way to associate that question with my account? For more information, visit "" in the . a.k.a. How can you link a registered account to a cookie-based account? a.k.a. How do I merge an unregistered account with a registered account a.k.a. Merging users a.k.a. How do I associate anonymous questions I’ve asked with my registered account? a.k.a. Is there a way to claim an unregistered user? (in case anyone searches with those terms) |
I know this question has been asked a million times before but I have checked out the previous posts and none of the advice given in them has worked for me. I'm getting this with the medibuntu repository. I'm running Xubuntu 12.04 so I know it's not an EOL issue. My internet connection is fine. I'm using it at the same time I'm doing the update. I'm able to surf the net, etc. I have a proxy but if that was the issue wouldn't all the repositories and PPAs be affected? Also, I've never had issues with the proxy server doing this before. This is the first time I have run across this error. I changed servers twice to different servers. I tried to select the best server and I tried the main server I tried the following three commands all without error sudo apt-get autoclean, sudo apt-get clean, and sudo apt-get autoremove. Then I tried running the update again and it still came up with the 404 error I ran sudo apt-get update | grep NO_PUBKEY and it just came up with the same error message I don't know what else to do at this point. | PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown: W: Failed to fetch http://ppa.launchpad.net/ 404 Not Found How do I fix these errors? |
In my project, I want to get all content of a SPListItem which is a calendar event. However, I have no idea to get them. using (SPSite site = new SPSite(@"http://spabc/")) using (SPWeb web = site.OpenWeb()) { SPList cal = web.Lists["Calendar"]; SPListItemCollection items = cal.Items; string texts = string.Empty; foreach (SPListItem item in items) { var xml = item.Xml; texts += xml; } lab.Text = "Event: " + texts;// it shows "Event: " } Target: Title, start Time, End Time, All Day Event, and Recurrence.. example of recurrence: Recurrence: Every 1 month(s) on the first Tuesday | Is there a way to get the text displayed for the "Recurrence" field on the View Item screen for an OOB "Event" list item through the object model? For example, I see: "Every 1 month(s) on the first Tuesday" Is there maybe a calculated field that I can reference using an SPListItem to get at this string (ensuring it's localized correctly)? For example: lblRecurrence.Text = item["RecurrenceText"].ToString(); Response targeted for SP2007, but interested if this carries over to 2010? Or if there is a way to get at it in 2010 that wasn't there before? |
I am facing a problem with JS object manipulation. I guess I know where is the problem but I cannot find a solution. I am trying to change the keys inside the objects from camel case to snake case (API requires snake case) by iterating over all of them inside the array. But when I change it, it makes a copy of it and does not affect the real object (console.log outside the loops). I hope it is clear, here is the code: for(user of allUsers) { for(key in user) { key = changeCase.snakeCase(key) console.log(key) //here it shows changed keys } } console.log(allUsers) // no changes in keys here | The primitive types (number, string, etc.) are passed by value, but objects are unknown, because they can be both passed-by-value (in case we consider that a variable holding an object is in fact a reference to the object) and passed-by-reference (when we consider that the variable to the object holds the object itself). Although it doesn't really matter at the end, I want to know what is the correct way to present the arguments passing conventions. Is there an excerpt from JavaScript specification, which defines what should be the semantics regarding this? |
I wrote a function in JavaScript, that replaces accents in a string to certain characters. function textToURL(str) { str = str.replace(/á/gi,'a'); str = str.replace(/é/gi,'e'); str = str.replace(/í/gi,'i'); str = str.replace(/ó/gi,'o'); str = str.replace(/ö/gi,'o'); str = str.replace(/ő/gi,'o'); str = str.replace(/ú/gi,'u'); str = str.replace(/ü/gi,'u'); str = str.replace(/ű/gi,'u'); str = str.replace(/ /gi,'-'); return str; } I'm sure there's a more clean and more simple way to write this code with arrays, or Regex, but how? Thanks in advance. | For a poor man's implementation of near-collation-correct sorting on the client side I need a JavaScript function that does efficient single character replacement in a string. Here is what I mean (note that this applies to German text, other languages sort differently): native sorting gets it wrong: a b c o u z ä ö ü collation-correct would be: a ä b c o ö u ü z Basically, I need all occurrences of "ä" of a given string replaced with "a" (and so on). This way the result of native sorting would be very close to what a user would expect (or what a database would return). Other languages have facilities to do just that: , in , , . But what about JavaScript? Here is what I have right now. // s would be a rather short string (something like // 200 characters at max, most of the time much less) function makeSortString(s) { var translate = { "ä": "a", "ö": "o", "ü": "u", "Ä": "A", "Ö": "O", "Ü": "U" // probably more to come }; var translate_re = /[öäüÖÄÜ]/g; return ( s.replace(translate_re, function(match) { return translate[match]; }) ); } For starters, I don't like the fact that the regex is rebuilt every time I call the function. I guess a closure can help in this regard, but I don't seem to get the hang of it for some reason. Can someone think of something more efficient? Answers below fall in two categories: String replacement functions of varying degrees of completeness and efficiency (what I was originally asking about) A of , which is now among JS engines (not so much at the time of the question) and could solve this category of problem much more elegantly. |
so I've successfully merged my 2/3 partitions into one and so now I have 2 partitions left, the one that I just merged cannot merge into my primary partition. It doesn't come up with the delete volume option in order for me to merge but only shrink volume. I've tried the Diskpart command prompt to try and force delete it but its jut kept on saying it was in use which it isn't. 32win7 is my primary and I just merged partition C and D together. thanks for the help Primary Partition is 48gb and Logical/extended drive is 250 | I am trying to delete my existing windows partition using disk management, when I am right clicked on the selected partition the 'Delete Volume' and 'Extend Volume' options are grayed out ( doesn't allow deletion and extension), and I can not also change or remove the drive letter of the disk which has above problem. And Another partition that I don't want to change anything it allows all the options. Why does this happen? |
Currently I am having USB 2.0 port Laptop. I am in the plan to buy USB 3.0 Pendrive/External Hard Disk. Whether USB 3.0 pendrive/ext HDD will support USB 2.0 Laptop's port? Or it will have problem to use? Thanks in advance. | I am planning to buy external hard drive that supports USB 3.0. Will it work with my old notebook that has USB 2.0? |
I want to install Ubuntu on a usb stick and run the OS from it and also use the same usb as main drive, like everything i install it's kept on there so then I'm able to run like "my user" on another computer. It's possible? | If you are hurrying to reply, System → Administration → StartUp Disk Creator -- no, that's not what I'm talking about. I want to try Ubuntu 11.04's Unity without touching my existing Ubuntu install. To do this, I need to install the nVidia drivers first (sigh). To do this, I need changes to persist a reboot. To do this, I need to really install Ubuntu on a USB key. How do you do that? What I tried I tried to make a USB key from , then boot from it, then choose "Install Ubuntu." The installer refused to install to the installation media itself. I tried, from my installed copy of Ubuntu: sudo kvm /dev/sdb --cdrom .cache/testdrive/iso/ubuntu_natty-desktop-i386.iso ...but the installer didn't detect the disk properly. |
We know that Yang Mills Theory forms the basis of the Standard Model of Physics, which describe the interaction of elementary particles at high energies, of course not including gravity. Yang Mills theory (gauge theory) and gravity are described by local invariance. String theory unifies gauge theory and gravity, what is the relation between gauge theory and gravity?. | Currently, (classical) gravity (General Relativity) is NOT a gauge theory (at least in the sense of a Yang-Mills theory). Why should "classical" gravity be some (non-trivial or "special" or extended) gauge theory? Should quantum gravity be a gauge theory? Remark: There are some contradictory claims in the literature to this issue. To what extent gravity is "a gauge" theory?Obviously, GR is not a YM theory. So, why do some people say that gravity "IS" a gauge theory? I found this question relevant, e.g., then we handle GR in the Einstein-Cartan theory or any other theory beyond GR, like teleparallel theories or higher-derivative gravitational theories. So I think it could be useful to discuss the "gauge flavor" of gravity here. |
When I'm busy, checking in to my flights via the web is often convenient. I get my boarding passes sent right to my phone and I don't need to worry about printing them before arriving to the airport. However, I also like collecting physical copies of my boarding passes. They're cool momentos of my travels more than anything else, and when I get the chance to print them out, I typically do. My question is, if I've already checked into my flight on my phone, can I print another set of boarding passes at the airport? I do like the official airport paper ones most. To make this question more general, consider the unfortunate situation of your phone dying. Having a backup physical copy of your boarding pass could save the day. In essence, is there anything stopping me from making another boarding pass at the kiosk after I've checked in beforehand? | I'm flying to Tokyo. The flight was sold through Finnair. The first leg is operated by American Airlines. The second and final legs are operated by Finnair. When I checked in online, it said that some airports on my journey (didn't say which one) don't allow mobile boarding passes?? Meaning I will need a physical copy. Unfortunately I don't have easy access to a printer. Will I still be able to print all my boarding passes at the airport even though I already checked in online? |
I am using 12.10. I am able to get my terminal with [super] + [w] keys but not with alt + tab keys. why is it invisible after minimizing the terminal. how can i correct it ? | I minimized my terminal after doing a repo sync. I cant find it on any desktop now! Please help. |
I purchased an iPhone 6s second hand and the person whom I purchased is now in London. (I am in India) When I restart the phone, it says this iPhone is currently linked to an appleID. When I asked the person what's the appleID of the phone, he says that it doesn't have any but the phone shows something like this : What do I do ? How do I get my phone to work ? Anyone please help I also tried putting the phone in DFU mode (press home button + lock button) and then installed the ipsw through itunes, still the above screen appeared. What can I do ? | I bought a used iPhone 4. The previous owner re-set the phone, but did not remove the device from their iCloud. It is asking me for their iCloud information when I try to set-up the phone. I don't have contact with the previous owner anymore. Is there a way to remove the device from their iCloud so I can use a new one? |
import numpy as np a = np.arange(6).reshape(2,3) np.meshgrid(*[np.arange(x) for x in a.shape]) What is the role of the asterisk before the parameter? why does it works? what dose it mean adding an asterisk before list comprehension as a parameter? | In the following method definitions, what does the * and ** do for param2? def foo(param1, *param2): def bar(param1, **param2): |
How can I find out who the originator of the email was or their location? I received a personal offensive email and I want to track who it came from? | How can I know where an email really originated from? Is there any way to find it out? I have heard about email headers, but I don't know where can I see email headers, for example in Gmail. Any help? |
I'm using iOS 5.1.1 (9B206). I want to upgrade my iPhone to iOS 6.1.3, but I don't know how to do this. I have tried downloading the IPSW of iOS 6.1.3 to upgrade, but it doesn't make any changes. The second time, I try building file SHSH with IPSW, but that didn't work either. Any ideas for this problem to upgrade from 5.1.1 (9B206) to ios 6.1.3 ? | I'm trying to downgrade my iPhone from the current iOS to an older one, as per . But every time I try, I always receive this error: The iPhone could not be restored. This device isn't eligible for the requested build. I have tried many times with and without DFU mode. Any ideas regarding this? |
My question is simple. In the classical mechanics, we know the least action principle does the variation on the action $$ S = \int (T-V) dt , $$ where $T$ is the kinetic term and $V$ is the potential term, to give the classical equations of motion. So why the least action principle extremizes (minimizes or maxmizes) this quantity $$T-V = H- 2V = E-2V =2 T- H = 2T-E?$$ Here I also denote $H$ as Hamiltonian. And $E$ as the energy of the system. In this regard, the $E$ is conserved, but not extremized. But $$E-2V =2T-E$$ is extremized! For example, if we write down the $(T-V)$ for a free falling object under constant gravitational acceleration $g$, we have $$T-V = \frac{1}{2} m \dot{y}^2 - m g y = E -2 m g y = m \dot{y}^2 -E$$ with $E=\frac{1}{2} m \dot{y}^2 + m g y$ is conserved. What is the physical significance of this $T-V$? (Provide good physical or math reasons.) I know how to derive equations of motion. I am asking a transparent way to understand why $T-V$ is in extremization. I suppose the extremization may minimizes or maximizes the action. (Not necessarily minimization, correct?) Do we have both examples of The equations of motion minimize the action? The equations of motion maximize the action? | Hamilton's principle states that a dynamic system always follows a path such that its action integral is stationary (that is, maximum or minimum). Why should the action integral be stationary? On what basis did Hamilton state this principle? |
I am new to latex. I am trying to add bibliography using .bib file. I have tried using \cite{} command to add the citation. But when I compile it it is showing question marks. Can someone tell me how can I add a citation in latex. I have used the following commands: \bibliography{references} \bibliographystyle{ieeetr} references.bib is the name of the .bib file | I've browsed the forums and found a number of posts that have addressed this issue, but none of the solutions seem to work for me. I have the following script that I just copied from the bibtex home page to get familiar with it. Instead of the citation number I get a question mark. I compile using Latex+Bibtex+Latex+Latex+PDFLatex+ViewPDF just as has been previously suggested and the problem persists. \documentclass[11pt]{article} \usepackage{cite} \begin{document} \title{My Article} \author{Nobody Jr.} \date{Today} \maketitle Blablabla said Nobody ~\cite{Nobody06}. \bibliography{mybib} \bibliographystyle{plain} \end{document} My bibliography (Bib.bbl) @misc{ Nobody06, author = "Nobody Jr", title = "My Article", year = "2006" } Looking at previous posts one thing that is concerning is that my .bbl looks empty as shown below. Further, I don't have a .blg \begin{thebibliography}{} \end{thebibliography} |
I have problems when using XMLHttpRequest. One occurs in Chrome; the other in firefox xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4) { if (this.status == 200) elmnt.innerHTML = this.responseText; } if (this.status == 404) { elmnt.innerHTML = "Page not found."; } } } xhttp.open("GET", file, true); xhttp.send(); I'm working locally, i.e. all protocols are file:// In chrome, where I have added parameter --allow-file-access-from-files, this.status is 0. Why? In firefox, the status is 200, but there will be a XML parsing error when the included file has code like this: <script> alert(-1<1); </script> and an XML parsing syntax error occurred indicating 10th character. Why? I guess firefox does not recognize '<' between script. Are they bugs or some issues I don't know yet? | Are CDATA tags ever necessary in script tags and if so when? In other words, when and where is this: <script type="text/javascript"> //<![CDATA[ ...code... //]]> </script> preferable to this: <script type="text/javascript"> ...code... </script> |
I am using macOS High Sierra V10.13.6. I can set up my custom environment variables in .bash_profile. But where is the system default environment variables are stored in the mac system For Ex: If i type echo $HOME in terminal i get the output as /Users/parithibang Where is this $HOME variable is been set up in the Mac Machine? In which path this is been set? | We used to use /etc/environment to set system-wide environment variables on Mountain Lion. However, it seems this file is no longer read. Ideally the solution should apply to all users, and we need it to work with ssh console sessions. So we need this to work ssh user@mavericks-machine 'echo $MY_ENV_VAR' So far we've tried: /etc/launchd.conf Works for all users, but only applies to 'windowed' applications, i.e. works in Terminal, but not in an ssh session. ~/.profile, ~/.bash_profile etc. Only applies to shells Any suggestions? |
I am an Indian citizen going to the UK in June on visitor visa, multiple entry valid until October. On my return journey, I have a layover of 12 hours and 15 minutes, and I also have to change planes from KLM to Jet Airways. Do I need a transit visa? Is there any option that I can get visa for 12 hours (short stay visa or transit visa) at the Amsterdam airport itself? | I found many related questions on this site but I am still not sure about the rules. How can I decide if I need a visa to transit? Schengen members as of May 2021 are as follows: Austria Belgium Czech Republic Denmark (excluding Greenland and the Faroe Islands - but an open border with the Schengen Area is maintained) Estonia Finland France (excluding overseas departments and collectivities) Germany Greece Hungary Iceland Italy Latvia Liechtenstein Lithuania Luxembourg Malta Netherlands (excluding Aruba, Curaçao, Sint Maarten and the Caribbean Netherlands) Norway (excluding Svalbard) Poland Portugal Slovakia Slovenia Spain (except Ceuta and Melilla) Sweden Switzerland |
The panel that appears as shown in the image below, cannot be re-opened. It only appears, on the left-hand-side of the screen when I create a new object. How do I get it back as shown in the image? My "Data" tab, looks different. | When you first add a cylinder, you have the option to change the number of vertices, etc, but once you do anything else in blender, it seems you no longer can edit those parameters. Is there a setting anywhere or an add-on that allows these parameters to be edited later on? If not, how easy would such an addon/feature be to create for anyone reading this? |
i need an overloaded method that uses enhanced for loops to build and return a String that contains the elements in an array. This is my work: public static String arrayToString(double[] dblArray) { String str = ""; for (double i : dblArray) { System.out.println(dblArray.toString()); } return str; } And i got output something like this: [D@232204a1 [D@232204a1 [D@232204a1 [D@232204a1 I think this is adress of array's elements. | In Java, arrays don't override toString(), so if you try to print one directly, you get the className + '@' + the hex of the of the array, as defined by Object.toString(): int[] intArray = new int[] {1, 2, 3, 4, 5}; System.out.println(intArray); // prints something like '[I@3343c8b3' But usually, we'd actually want something more like [1, 2, 3, 4, 5]. What's the simplest way of doing that? Here are some example inputs and outputs: // Array of primitives: int[] intArray = new int[] {1, 2, 3, 4, 5}; //output: [1, 2, 3, 4, 5] // Array of object references: String[] strArray = new String[] {"John", "Mary", "Bob"}; //output: [John, Mary, Bob] |
I have a Dell Inspiron 15 (5000 series) and am trying to dual-boot Windows 10 (already installed) and Ubuntu 16.04.3 LTS. I have a bootable USB stick, which I made using the ISO file from Ubuntu's website, and UNetBootIn (I have also tried this with a stick made from Rufus). However, when I try to boot from the USB to install Ubuntu, I am unable to do so. I have tried booting from a USB drive on Legacy BIOS, which does start booting up Ubuntu, but it freezes a few seconds into the boot process. I have also tried booting on the standard UEFI, but adding grub (specifically, EFI/grubx64.efi on my USB stick) as a boot option. Note that when I do this, I disable Secure Boot. This does bring me to the standard grub screen, and I can click "Try Ubuntu without Installing", but it freezes on the load screen. Any advice would be greatly appreciated! :) Thanks in advance! | This is the third time I've tried to install Ubuntu Server 14.04.03 64-bit on the same laptop, and each time it caused different problems. Each time I wrote the same iso image to a USB flash drive by using a different application and OS. Universal USB Installer (pendrivelinux.com) from Windows WinImage writer from Windows built-in image writer from Linux Mint 17.2 The iso image is the same in all three cases, the USB flash drive is the same, and the laptop is the same. However each time the installation of Ubuntu gave me different installation options. For example, the last time I installed Ubuntu, it didn't show all the packages to choose while installing (Basic Ubuntu server, etc.). |
The spell Melf's Acid Arrow does 4d4 on hit and 2d4 next turn (I'm ignoring what happens for a miss). If you roll a 20 for your spell attack roll, you double the 4d4 to 8d4. What about the 2d4 next turn? Does that get doubled too or does that just stay at 2d4 because it occurs on the next turn? I know that covers additional kinds of damage during a critical hit, but this is the same substance that did critical damage, continuing its damage in a later round. | I'm a bit confused on how extra damage works for critical hits. Let's take the following example: A thief with sneak attack rolls a crit. I'm under the impression he rolls double his normal attack damage dice AND double his Sneak Attack damage dice. Is this accurate? Another example, I finished DM-ing my first campaign recently. The Giant Spider enemy monster has an melee attack that causes a constitution saving throw. If the player fails, the enemy rolls an additional 2D8 of damage. In this situation, if there was a critical hit, and the player failed their saving throw, would I also roll double dice on the additional damage? Or is that considered a separate attack? |
I have an external hard disk drive that I have set to drive F which contains some programs that I have shortcuts on the desktop to. I have a second external hard disk drive which I store my music on which is auto assigned to drive E, due to someone thinking that Australians love to have wings on power plugs for hard drives while power boards have each socket close together. I can have both of these hard drives set at the same time. My music hard drive I normally only plug in when I synchronise music to my iPod, but on occasion when I unplug my music hard drive and plug my old one back in or at times when I turn on my computer with the music hard disk drive in, turn off my computer and turn it back on with my old hard drive, its drive letter gets switched to E. I get annoyed having to always go into disk management and change the drive letter back to F when this happens so Can I lock my hard drive to always be F? If anything else tries to be F, it can fail for all I care. Is there a batch file I can use that'll go though all the steps of Disk Management to change a drive's letter, that way I can set it up in the startup folder? EDIT: I get annoyed having to always go into disk management and change the drive letter back to F when this happens I am just pointing it out in case someone missed it, because I already use Disk Management to change the drive letter back to F. If it stayed there then I would have a problem. | I have scripts that expect specific drive letters for hard drives. Windows sometimes assigns the different drive letters (e.g. I expected my Maxtor drive to be E:, but it's now F:, therefore my scripts will fail), depending on the order of how the drives are plugged into my laptop. In Windows 7, how do I assign a permanent drive letter to a drive? |
There are so many things wrong with LaTeX2e according to the latest discussion, , from documentation to speed, inflexible kernel, etc. We are perhaps waiting in vain for LaTeX3 and expl3 full deployment but what is called "gentle re-fractory" see . What are the deficiency and features in LaTeX2e that LaTeX3 project hence "gentle refractory" and L3 programming seeks to provide solution to (and how significant )? Surely separating design and codes will be great, but LaTeX3 project must prove it's relevance in terms of quality of extension, alternate solutions, user interface and better features than LaTeX2e! Secondly, I haven't seen any basic and compilable Tex for mobiles OS like android. Many use online Tex Editors and tools or snippets like Overleaf. Will need latest implementation of TeX on say android OS and MacOS. In my opinion, LaTeX3 project has taken so much time, (more than 20years since the project started), and surlely new issues of change due to time will continually postpone "getting perfected for release" Sure, it won't be able to replace LaTeX2e and conTeXt but "soft refractory" for possible modernization I find information on the following discussions partly useful and educating.. . . Am currently working on mobile implementation of TeX-Latex. | There are a few questions on this forum asking about why Latex3 is taking so long to come out. However, all of these are from the early 2010s. I'm just wondering what the current state of the project is and whether it's ready (or nearly ready) for prime time? |
Get:2 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libxatracker2 amd64 17.0.7-0ubuntu0.16.04.2 [1,106 kB] Err:2 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 libxatracker2 amd64 17.0.7-0ubuntu0.16.04.2 Hash Sum mismatch Get:1 http://archive.ubuntu.com/ubuntu xenial-security/main amd64 firefox amd64 57.0+build4-0ubuntu0.16.04.5 [43.6 MB] Err:1 http://archive.ubuntu.com/ubuntu xenial-security/main amd64 firefox amd64 57.0+build4-0ubuntu0.16.04.5 Hash Sum mismatch Fetched 88.4 MB in 3min 20s (441 kB/s) E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/f/firefox/firefox_57.0+build4-0ubuntu0.16.04.5_amd64.deb Hash Sum mismatch E: Failed to fetch http://archive.ubuntu.com/ubuntu/pool/main/m/mesa/libxatracker2_17.0.7-0ubuntu0.16.04.2_amd64.deb Hash Sum mismatch E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing? | When I check for updates, I get a "Failed To Download Repository Information" error. This is what comes up under details: W: Failed to fetch gzip:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_natty_main_source_Sources Hash Sum mismatch, E: Some index files failed to download. They have been ignored, or old ones used instead. |
I am trying to include a page of another pdf (in another folder) into a TeX file as it compiles. The other document has spaces in the title as well as in the path. \documentclass[12pt]{article} \usepackage{grffile} \usepackage{pdfpages} \begin{document} \includepdf[pages=6]{../AP Exams/2005 Form A/2005AFRQv2} \end{document} I end up with an off-center image of the page preceded by the path in the command on the left side. Does anyone know how to fix this? I'm using XeLaTeX for reasons not shown in this MWE. | I am trying to use \includepdf with about 20 different PDFs. The first 19 have worked fine, but the last one which can be found below will not load properly. However, there are no errors - the PDF produced just has a blank page with a couple of black lines in the middle. I converted the PDF to JPG and used \includegraphics and it loaded properly but then I could not add it to my table of contents in the way I wanted. Any thoughts on why it won't load as a .pdf but will as .jpg? Here's a minimal document that shows the problem: \documentclass{article} \usepackage{pdfpages} \begin{document} \includepdf{analysiscompsSprJan2011.pdf} \end{document} |
How do I solve this definite integral? $$I =\int_{-2}^2 \frac{x^2}{1+5^x}dx $$ Is there any way to solve this integral using high school calculus. P.S This was asked in the recently conducted CBSE Exams in India. | $$\int^2_{-2}\frac{x^2}{1+5^x}$$ How do I start to integrate this? I know the basics and tried substituting $5^x$ by $u$ where by changing the base of logarithm I get $\frac{\ln(u)}{\ln 5}=x$, but I got stuck. Any hints would suffice preferably in the original question and not after my substitution. (And also using the basic definite integrals property.) Now I know only basic integration, that is restricted to high school, so would prefer answer in terms of that level. |
I saw that some quite similar questions have already been asked on the forum, but, still, I can't find a way to solve my problem. I've just installed the mactex package 2015 from and then installed TeXworks. Now, when I try to compile any file I get the following error message: It's in italian and it means that program "pdflatex" has not been found and that I need a TeX distribution like MacTex. The point is that I've already installed the Mac distribution! Any help? | Now here is the thing. I upgraded my Mac to the OS X EI Capitan a few days ago. And now MacTeX is not working. When I try to typeset it, the console shows the following error: xelatex: command not found. How can I fix it? |
Do you know how to recover media files from iPhone 6? I lost my photos and music by some accident. | I used an iPhone 3G from May of 2009 until around the spring of 2013, at which time I upgraded to the iPhone 5. I've always been a prolific iPhotographer :) and recently pulled around 12,000 photos off my iPhone 5 for backup and to free up disk space. I've kept the old iPhone 3G, though, and suspect it has thousands of pictures on it that need to be removed from the phone and backed up on my cloud, my laptop, and an external hard drive. However, Apple no longer makes available the OSX that supports and grants access to an iPhone 3G through iTunes. I can't hook it up to my laptop (Dell XPS 15Z, if it helps to know what I'm running, with Windows 7) and access the pictures to manually move them off the phone. How do I recover pictures from an iPhone 3G? Is there anything that can be done? Is there anything that can be done? As it is, I can't get my computer to even see the 3G, much less charge the phone through the computer or allow me to access the phone's drives and my pics. I'm currently charging the 3G via wall plug/USB, which I think will allow me to look at my photos on the phone itself once the phone is juiced up ... but I really just want to recover and transfer my images off the iPhone 3G for safekeeping. I did search this site prior to posting and could not find my exact question. Please don't hesitate to VTC if I've accidentally submitted a duplicate. |
Hi I have a python code written as followed. Can someone please explain what these colons do? edges = (data[0,0:-1]+data[0,1])/2.0 counts = data[1,1:] | I need a good explanation (references are a plus) on Python's slice notation. To me, this notation needs a bit of picking up. It looks extremely powerful, but I haven't quite got my head around it. |
I am writing my minor thesis which includes a number of tikz figures, which are all listed in a table of figures. the table of figures gives the figure number, and then the title of the figure, as given by the caption. the way i have put them into my document is in the following manner: % ---------------- \begin{figure}[h!] \centering \includegraphics{./tikz/network.tikz} \caption{Feed-forward neural network - The red line indicates the path a signal travels from input node $x_2$ to output node $y_4$.} \label{fig:network} \end{figure} %----------------- My problem is that the whole caption is being printed in the list of figures, and i would like it only to have "Feed-forward neural network" in the list of figures. I would be greatly appreciative if someone could explain to me how i can separate the figure title from extended description. thanks | I am using the 'article' class, 'figure' environment. My captions are divided in two parts: the information about the figure the credits of the figure (for which I use \textfff{}) In my list of figures, I would like to omit the second part. Would you have a solution, please? |
Prove that if $n\geq1$ then $$\binom{2n}{n}=\sum_{k=0}^{n}(\binom{n}{k})^2$$ This is what I have so far: By the Binomial Theorem: $$\binom{2n}{n}=\frac{(2n)!}{(2n-2)!n!}=\frac{2n!~}{n^2(n-1)^2(n-2)^2...1}$$ By the definition of summation: $$\sum_{k=0}^{n}(\binom{n}{k})^2=(\binom{n}{0})^2+(\binom{n}{1})^2+(\binom{n}{2})^2+(\binom{n}{3})^2+...+(\binom{n}{n})^2$$ By the Binomial Theorem => $$\sum_{k=0}^{n}(\binom{n}{k})^2=1^2+(\frac{n!}{(n-1)!})^2+(\frac{n!}{(n-2)!2!})^2+(\frac{n!}{(n-3)!3!})^2+...+1^2$$ $$=1+\frac{n!n!}{((n-1)!)^2}+\frac{n!n!}{((n-2)!)^2(2!)^2}+\frac{n!n!}{((n-3)!)^2(3!)^2}+...+1$$ This is where I get stuck. I'm not sure how to continue from here. I know that what I am getting is starting to look a lot like what I want it to look like but I don't know how to finish, nor am I sure that I've done it correctly to this point. Help? | I was hoping to find a more "mathematical" proof, instead of proving logically $\displaystyle \sum_{k = 0}^n {n \choose k}^2= {2n \choose n}$. I already know the logical Proof: $${n \choose k}^2 = {n \choose k}{ n \choose n-k}$$ Hence summation can be expressed as: $$\binom{n}{0}\binom{n}{n} + \binom{n}{1}\binom{n}{n-1} + \cdots + \binom{n}{n}\binom{n}{0}$$ One can think of it as choosing $n$ people from a group of $2n$ (imagine dividing a group of $2n$ into $2$ groups of $n$ people each. I can get $k$ people from group $1$ and another $n-k$ people from group $2$. We do this from $k = 0$ to $n$. |
Want to get the IP address using Shell script. Without knowing the eth0 or eth1 or eth2 How to get the particular IP address. I am not interest to get localhost address, want to get private IP address. | I need to find my external IP address from a shell script. At the moment I use this function: myip () { lwp-request -o text checkip.dyndns.org | awk '{ print $NF }' } But it depends on perl-libwww, perl-html-format, perl-html-tree installed. What other ways can I get my external IP? |
Is there a way for me to obtain my 5th gen pokemon without.. A) Using the Pokebank. B) Trading each pokemon individually with a willing friend? | I know that you can trade Pokemon between games of the same generation (Gold/Silver, Ruby/Sapphire) and even trade between 1st gen and 2nd gen. However, I haven't been able to find a way to trade Pokemon so that I can play with my 1st generation Pokemon in HeartGold, for instance. If it is possible, how many steps would it take and what equipment would I need? |
Tried Remmina (VNC) but only managed to do it on the local network. | How do I remotely control another desktop (both are Ubuntu 12.04) from my client machine? Is it possible to use Remmina Remote Desktop Client? |
I was sleeping in the dark when I reached over for my blanket. It slipped out between my fingers and made a light spark. I repeated in different parts of the blanket at least ten times. I can't understand why this is happening. I rubbed another blanket and my fingertips still sparked. Why does this happen? | Sometimes when I'm in bed at night, I rub my feet against the sheets and light is created. What exactly is going on? I'm familiar with static electricity, and the triboelectric effect (creating a charge by rubbing 2 insulators together), and electrostatic discharge (releasing charge by touching a grounded conductor). I believe that all of that is what is at work here, but I'm slightly confused since in other cases, the triboelectric effect and electrostatic discharge seem to occur as two separate steps, with different substances involved, and here, the two effects seem to be occurring simultaneously, with the same substances. Can someone help me with a step-by-step explanation of the dynamics of what is going on? |
I cannot comprehend why there are so many games available for windows and so few for linux in comparison. Why is the main reason, is it a technical or business reason ? Are Windows libraries (directx) better or is it because of the driver support ? Linux have some great libraries like Allegro , SDL and LibGlut. And Android is Linux after all. Given all that Why are more games in windows than linux ?. | What is wrong with the Linux/*nix family for games? What makes the development of games for this platform too slow compared to Windows or even OS X? |
$(X,d)$ metric space and $A\subset X$ and $A$ is connected. $$ \text{Card}(A) > 2 \implies \text{Card}(A) \geq \text{Card}(\mathbb{R}).$$ How do I prove it ?Waiting for your help? | As the topic, how to prove that every connected metric space with at least two points uncountable? Of course i know the definition that a countable set mean there is a bijection between the set and the positive integer. Connected is opposite of disconnected where the set can partition into two disjoint open sets. |
Does charge bend spacetime like mass? I'm not asking if electromagnetic forces can be described geometrically, but if EM fields could correspond to particular curvatures of spacetime, like gravity which arises from the spacetime bending due to the stress-energy tensor. Is it true in the three spacial dimensions we observe? Is it plausible in other dimensions (for example the fourth dimensions of the Kaluza-Klein theory)? | It is written everywhere that gravity is curvature of spacetime caused by the mass of the objects or something to the same effect. This raises a question with me: why isn't spacetime curved due to other forces or aspects of bodies? Why isn't it that there are curvatures related to the charge of a body or the spin of particles or any other characteristics? |
I have Ubuntu 17.04 on my Asus laptop. After login I cannot write anything to /dev/sda6 It tells me that the disk is in read-only mode: How can I fix it? | Whenever I boot Ubuntu, I get a message that it cannot mount my windows partition, and I can choose to either wait, skip or manually mount. When I try to enter my Windows partition through Nautilus I get a message saying that this partition is hibernated and that I need to enter the file system and properly close it, something I have done with no problem so I don't know why this happens. Here's my partition table, if any more data is needed please let me know. Device Boot Start End Blocks Id System /dev/sda1 2048 20000767 9999360 83 Linux /dev/sda2 20002814 478001151 228999169 5 Extended /dev/sda3 * 478001152 622532607 72265728 7 HPFS/NTFS/exFAT /dev/sda4 622532608 625141759 1304576 82 Linux swap / Solaris /dev/sda5 20002816 478001151 228999168 83 Linux |
Let $f$ be a continuous function on $\mathbb R$ satisfying the relation $$f(f(f(x))) = x\ \text{for all}\ x \in \mathbb R$$ Prove or disprove that $f$ is the identity function. I tried taking the derivative. From the derivative, I'm not sure about it, but I concluded it had to be of degree 1 if it is a polynomial since if it'd have been of degree 2 or higher.. there needed to be terms of $x$ in the derivative.. which are not there. | Does $f(f(f(x)))=x \implies f(x)=x$? Is it necessary for it to follow? How do we prove this? Do we have to substitute some special $x$? Or is it some other consideration of its properties? Edit: does it follow in the special case when f is surjective? Or would we wind up with the same thing? |
/*Edited: For Blender 2.7 Users I found a detailed with pictures. */ I want to build an VR-Scene in Unity with a little Island and and ocean around. For the ocean I am quite happy with the ocean modifier and made already an looping animation with the water. But I simply cannot find a solution to export the mesh + animations to Unity. I keyframed the time and scale and found the problem, that these can't update when I apply the modifier. To my understanding blender needs to apply the modifier when exporting, so I can even get the shape of Ocean. [ I tried and failed with explanation. Could somebody please give me an more beginner friendly explanation? Here is my blendfile: | It is there any way to export the foam data generated from ocean modifier to use it in other render engine, like LuxRender? The manual says that the foam data is stored as vertex color data, but there isn't a way to access the vertexColor data. I know that can be accessed from Cycles from attribute's node. LuxRender supports vertex color and I tried to bake the texture to vertexColor and an image but only get a plain black texture. |
All I want to do is load information I saved to a plain text file about the position of a and set the frame to the state it was saved as. For some reason I'm unable to compare capture groups with strings; that is, matcher.group("state") compared to the string it should be ("min", "max", or "normal") is not returning true, and the same goes with matcher.group("vis"). String fileArrayStr = "WINDOW_LAYOUT:0,0|779x768|max|show" My code is: byte[] fileArray = null; String fileArrayStr = null; try { fileArray = Files.readAllBytes(PathToConfig); } catch (IOException e) { e.printStackTrace(); } try { fileArrayStr = new String(fileArray, "UTF-8"); } catch (UnsupportedEncodingException e) { e.printStackTrace(); } // checking the value of fileArrayStr here by outputting it // confirms the data is read correctly from the file pattern = Pattern.compile( "WINDOW_LAYOUT:\\s*" + "(?<x>[0-9\\-]+),(?<y>[0-9\\-]+)\\|" + "(?<length>\\d+)x(?<height>\\d+)\\|" + "(?<state>[minaxorl]+)\\|" + "(?<vis>[showide]+)\\s*"); matcher = pattern.matcher(fileArrayStr); if (matcher.find()) { frame.setLocation(Integer.parseInt(matcher.group("x")), Integer.parseInt(matcher.group("y"))); frame.setSize(Integer.parseInt(matcher.group("length")), Integer.parseInt(matcher.group("height"))); DialogMsg("state: " + matcher.group("state") + "\n" + "vis: " + matcher.group("vis")); // the above DialogMsg call (my own function to show a popup dialog) // shows the // data is being read correctly, as the values are "max" and "show" // for state // and vis, respectively. Same with the DialogMsg calls below. if (matcher.group("state") == "min") { try { frame.setIcon(true); } catch (PropertyVetoException e) { e.printStackTrace(); } } else if (matcher.group("state") == "max") { try { frame.setMaximum(true); } catch (PropertyVetoException e) { e.printStackTrace(); } } else { DialogMsg("matcher.group(\"state\") = \"" + matcher.group("state") + "\""); } if (matcher.group("vis") == "show") { frame.setVisible(true); } else if (matcher.group("vis") == "hide") { frame.setVisible(false); } else { DialogMsg("matcher.group(\"vis\") = \"" + matcher.group("vis") + "\""); } } The code is always falling back to the else statements. What am I doing wrong? is supposed to return a string, is it not? | I've been using the == operator in my program to compare all my strings so far. However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug. Is == bad? When should it and should it not be used? What's the difference? |
I have 8 gb of ram and use my machine for web browsing streaming and some light gaming. Do I need a swap partition? | I have read , but it was asked in the context of servers not desktops or notebooks. If a good amount of RAM is installed on a notebook, say 8 GB, do we still need a swap space? |
I am having trouble understanding this question. I know the total number of function is $4^6 = 4096$. There are no injective functions as the domain > co domain. I know there is a part that I'm missing that has to do with the amount of functions that are neither surjective nor injective. My train of thought was along the lines of (total - injective (=0) - not injective not surjective) = total number of surjective. | Let $m,n$ be two integers such that, $m\ge n$. Compute the number of surjections from $\{1,...,m\}$ to $\{1,...,n\}$ There are $n^m$ functions (total). we subtract from $n^m$ the number of non-surjective functions. There are $\binom{n}{1}(n-1)^m$ functions missing one element. There are $\binom{n}{2}(n-2)^m$ functions missing two elements, but how many times did we count this in the previous count ? Then we have to add this again by inclusion-exclusion but why is the difference always 1? |
A dir I cd into a lot has a really long path. I'd like to reduce keystrokes. I have tried this... sudo ln -s /mnt/c/Users/me/ho/hum/bin /mybin It works, but something about it seems wrong. Is there a better way? I currently use bash, but a solution that would still work if I switched shells would be nice. System info Running Unbutu on Windows Subsystem for Linux. $ uname -a Linux Hostname 4.4.0-17763-Microsoft #253-Microsoft \ Mon Dec 31 17:49:00 PST 2018 \ x86_64 x86_64 x86_64 GNU/Linux | I would like to frequently switch between directories that are in totally unrelated paths, for example /Project/Warnest/docs/ and ~/Dropbox/Projects/ds/test/. But I don't want to type cd /[full-path]/ all the time. Are there any shortcut commands to switch to previously worked directories? One solution I could think of is to add environment variables to my bash .profile for the frequently used directories and cd to them using those variables. But is there any other solution to this? |
I am writing my thesis in draft mode. \documentclass[dissertation,draft]{univthesis} The univthesis is a dissertation template like a book. However, when I include figures, I only see the figure name and box enclosing it. When draft mode is removed, I get what I want. So, I was wondering if there is a way to display images even in draft mode. I have both .eps and .pdf files in the current directory. | For collaboration purposes I am using the draft mode in my LaTeX manuscript to show todo-notes, remarks and so on. By switching to final mode all of these additions become unvisible. However, I'd love to switch on the final mode of the graphics/x package to see the actual pictures but \documentclass being still in draft mode. I get an error about clashing options when I add \usepackage[final]{graphicx} My first guess was that the \documentclass already sets the option for the graphics/x package. Following doesn't help either \PassOptionsToPackage{final}{graphicx} \documentclass[twoside,onecolumn,draft]{rsauthor} |
I tried using the cases to code this, but I only can put them in two separate lines, not along the same line. | I want to write a conditional expression such as the following. What is the best way to express such conditional expressions in Latex? |
I want to get the image associated to a file based on the extension. for example: \100xadmin\100xredirectedfolders$\elianf\Desktop\WORK\Query Coalesce.txt I just want to get image related with .txt extension. | I have a form that displays file information in a TabControl, and I'd like the pages to have the file's icon in their tab. How do I get the icon associated with a file type? I'd prefer solutions that don't involve looking things up in the registry, but if that's the only way then so be it. |
I want to show Frame Number/Total Frame Number without navigation bar, just like the following picture: The below MWE works as expect: \documentclass{beamer} %\usetheme{Copenhagen} \beamertemplatenavigationsymbolsempty \setbeamertemplate{footline}[frame number]{} \begin{document} \frame { \frametitle{Frame A} Frame A } \frame { \frametitle{Frame B} Frame B } \frame { \frametitle{Frame C} Frame C } \end{document} However, if I uncomment the second line %\usetheme{Copenhagen}, the Frame Number/Total Frame Number disappears as follows: My compiler is TexLive 2018 with xelatex. Is there any way to show Frame Number/Total Frame Number with Copenhagen theme? | The following MWE does not print frame numbers with MacTeX 2017 (beamer v3.50, LuaTeX 1.0.4): \documentclass{beamer} \usetheme{PaloAlto} %\beamertemplatenavigationsymbolsempty \setbeamertemplate{footline}[frame number] %\setbeamertemplate{page number in head/foot}[framenumber] \begin{document} \begin{frame} \frametitle{Test} Bar \end{frame} \end{document} But it works with TeXLive 2016 (beamer v3.41, LuaTeX 0.95.0): Using setbeamertemplate{page number in head/foot}[framenumber] instead of \setbeamertemplate{footline}[frame number] does not help. How can I fix it? |
Give a generalized form [in the form of "n" i.e number of vertices of a polygon] of the number of combinations possible for 3 colored balls [infinite balls [it is not compulsory to use all the colors]] to be placed at vertices of a polygon with n vertices. The condition to be met is that no balls of same colored to be placed adjacent to each other. We consider two colorings the same if the can be obtained from one another by rotating or reflecting the n-gon. Conditions: No two same colors can be placed adjacent We have only 3 types of balls and which can be used in any number as far as 1st condition is followed. Rotation or reflection pf a coloring does not count as a new coloring. Eg: Take a case of Triangle. Possible combinations of placing balls is 1 i.e. 1 ball of each color. Square: we can take either 2 balls each of 2 different colors or 2 balls of one color, 1 ball each of other two colors. Which gave total combinations of 6. | Given an $n$-sided polygon, how many ways can you color the vertices using $k$ colors so that no two adjacent vertices have the same color? (Inspired by 2011 AMC 12 A #16 – I'm able to do this for small cases but not in general.) |
If the roots of the equation $x^3-x+1=0$ are $a$, $b$ and $c$, then find the value of $a^5+b^5+c^5$. My attempt: I found out $a^2+b^2+c^2$ and a$^3+b^3+c^3$ but it is turning out to be extremely lengthy to find the sum of the roots raised to the $5^{th}$ power. | Can someone please help us solve this equation. It was on our college entry exam, but no one managed to solve it. The problem is: Let $p,q,r$ be the roots of $x^3 -x+1=0$. Then $p^5+q^5+r^5 = ?$ Correct answer was $-5$, but no one managed to solve this problem. We tried different methods, but none came up with a solution. Any help is appreciated. |
I am beginning to study general relativity and one of the preconceptions that I have is that massive objects will warp space in a similar way to that described by the photo below However my understanding is that massive objects in fact warp spacetime and that in a time and spatial coordinate system straight lines might not be straight due to the presence of massive objects. Does this imply the warping of space as above? And if not, how can you explain the bending of light around massive objects? | I've seen many science popularisation documentaries and read few books (obviously not being scientist myself). I am able to process and understand basic ideas behind most of these. However for general relativity there is this one illustration, which is being used over and over (image from Wikipedia): I always thought that general relativity gives another way how you can describe gravity. However for this illustration to work, there needs to be another force, pulling the object down (referring to a direction in the attached image). If I put two non-moving objects in the image, what force will pull them together? So where is my understanding incorrect? Or is general relativity not about explaining gravity and just describes how heavy objects bends spacetime (in that case the analogy is being used not correctly in my opinion)? UPDATE Thank you for the answers and comments. Namely the XKCD comics is a spot on. I understand that the analogy with bent sheet of fabric pretty bad, but it seems that it can be fixed if you don't bent the fabric, but just distort the drawn grid. Would you be so kind and answer the second part of the question as well - whether general relativity is explaining gravitational force. To me it seems that it is not (bending of spacetime simply can not affect two non-moving objects). However most of the time it is being presented that it does. |
Now since Photons have energy too, is it possible for these particles to gravitationally attract each other. | In general relativity, light is subject to gravitational pull. Does light generate gravitational pull, and do two beams of light attract each other? |
Show that the set $ [-1, \infty )$ has cardinality of the continuum. Draw the bijection. Answer: If I consider the map $ f: [-1, \infty ) \rightarrow (-\infty, \infty) $ by $ f(x)=\log(1+x) $. This is one-one and onto. Hence the proof. But I have doubts using $ f(x)= \log(1+x) $ because it is not defined at $ x=-1 $. Any help is there ? | How to define a bijection between $(0,1)$ and $(0,1]$? Or any other open and closed intervals? If the intervals are both open like $(-1,2)\text{ and }(-5,4)$ I do a cheap trick (don't know if that's how you're supposed to do it): I make a function $f : (-1, 2)\rightarrow (-5, 4)$ of the form $f(x)=mx+b$ by \begin{align*} -5 = f(-1) &= m(-1)+b \\ 4 = f(2) &= m(2) + b \end{align*} Solving for $m$ and $b$ I find $m=3\text{ and }b=-2$ so then $f(x)=3x-2.$ Then I show that $f$ is a bijection by showing that it is injective and surjective. |
I have to create two algorithms (but I think it is more of a combinatorics question). Let there be list of permutations on elements $\{1,2,...,k\}, k \in N$ and this list is alphabetically ordered (meaning that e.q. permutations with $\pi(1) = 10$ is in this list before $\pi(1) = 2$). 1) Find position of specified permutation in that list - e.g. input is (1, 2, 4, 3, 5) and find position, it would give 3 2) Find what permutation lies in that list on specified position - e.g. input is 3 and I should find what permutation is on third line, that can be something like (1, 2, 4, 3, 5) I tried to approach this as counting permutations that can be before specified one, but it seems quite complicated since $k$ can be huge number... at least for me as a combinatorics newbie. Is there maybe some approximation that would give me some decent starting point from which I'd be able to start checking permutations manually and not having exponential time complexity? Thanks a lot! | I have an ordered set of symbols S = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9 }. I want to find the 1,000,000-th permutation in lexicographic order of S. It is a programming puzzle, but I wanted to figure out a way without brute-forcing the task. So my thinking was like this: For 10 variable symbol positions, we have 10! permutations, obviously. Now we want to find the first symbol. If we fix the first symbol, then the remaining 9 symbols can have 9! combinations. That means that 0 or 1 cannot be the first symbol, because the highest possible position is 2*9! = 725,760, which is lower than 1,000,000. The lowest position for a leading 3 is 3*9! + 1 = 1,088,641, so it can't be 3 or higher, either. Therefore, the first number must be 2. 2*9! is the largest multiple of 9! no greater than 1,000,000, so I need the 2nd symbol (zero-based) from the current set. So now the question becomes, of the remaining S := S \{2}, which permutation of these symbols is at lexicographic position (1,000,000 - 2*9!) = 274,240? 6*8! = 241,920 is the largest multiple of 8! which is smaller than 274,240, so I need the 6th-smallest symbol of the remaining set, which is 7. So the prefix should be 27 by now. That way, I keep going and finally arrive at: 1,000,000 = 2*9! + 6*8! + 6*7! + 2*6! + 5*5! + 1*4! + 2*3! + 2*2! + 0*1! + 0*0! which results in "2783905614" as my solution. However, according to the , (free reg. req.) that is incorrect. Where did I go wrong in thinking or applying? |
I have a log-in form that I want to validate and redirect (if the username and password are correct) with jQuery, and the redirect isn't working. This is my code: $(document).ready(function() { $('#lc-login').click(function() { var username = $('#username').val(); var pass = $('#pass').val(); if (testUser(username) === true && testPass(pass) === true) { window.location.replace("http://www.domain.com/home.html"); } else { alert('warning message'); } }); }); I've try replacing the window.location.replace with window.location.href and still nothing. I should say that the testUser and testPass are working fine, because if I add a simple alert('the validation is ok!'), the message is appearing on my screen. | How can I redirect the user from one page to another using jQuery or pure JavaScript? |
I've tried doing a WP_Query based on a custom field, which name is 'date' and value is something like '14/01/2015'. I want the query to give results when 'date' is between today and tomorrow. All I've tried so far is this: $y=date('d/m/Y',strtotime('yesterday')); $t=date('d/m/Y',strtotime('tomorrow')); $o=date('d/m/Y',strtotime('today')); echo "yesterday: ".$y; echo "today: ".$o; echo "tomorrow: ".$t; $d=new WP_Query( array( 'category__in' => array(4), 'post_type' => 'post', 'posts_per_page' => '-1', 'orderby' => 'meta_value', 'order' => 'DESC', 'meta_query' => array( 'key' => 'data', 'value' => array($y,$t), 'compare' => 'BETWEEN', 'type' => 'DATE', ) ) ); But is giving me posts which 'date' is also 25/01/2015. What am I doing wrong? Thanks in advice | I am building a WP site with an events feature. The events page was made with custom post types. I want to make it possible for people to search/ filter events by dates. For example, they can search for all events happening between 2nd December, 2011 and 1st March, 2012 and get results from events that have their dates between the months of December and March (ie. december, january, february and march). I want to know the best way to go about this. Any ideas? You can see an example of what I want to achieve by looking at the "Search events by date" feature on this page If that won't be possible, is there any way I can get them to search for events happening between certain months, say December and February(excluding the days)? Thanks in advance. |
I'm trying to get DOF in Compositing from an OpenEXR image with Combined/Alpha/Mist passes. This is the combined pass: I can get DOF by a defocus node using the Mist pass (after a ColorRamp to define better), but I can't set which part of the image is focused and unfocused. (I want the character with the knife to be focused, and not the other character). If I invert the Mist image I can achieve this but the borders aren't unfocused: Is there any better way to achieve this? FYI I have an alpha pass Thank you! | Is is possible to increase the depth of field in cycles while keeping the same blur size? I know this is not physically correct, but in some renders this would be useful. Here is a demonstration of what I am looking for: Normal Focus: What I'm trying to achieve (New part shaded green): Is this possible (Maybe with the compositor)? If so, how? Any help is appreciated. An example for what this would be used for would be the following: I have a somewhat lengthy main object that I want in focus. The other background objects are moderately close to the main object, but I want them to be blurred. If you increase the DOF blur to ensure the background objects aren't in focus, your main object is only partially in focus. The Depth of focus is too shallow to fit your main object. Now if you change to a wide DOF, the background objects would still be relatively clear which is not what you want. The solution is what I am describing; You would set a very shallow DOF, initially, so that the background is well out of focus, and then you would increase just the focus area to cover the main object but keep the blur amount the same. |
How can I install Google Chrome to a custom location, instead of its default usr/bin? And where does Chrome keep user settings? | When I install a software using apt-get it installs to default locations i.e to /usr/bin, /usr/lib, /usr/share and etc. For example when I install "Meld Diff Viewer" using sudo apt-get install meld and use whereis command to find its location, I get the following output adnan@adnan-laptop:~$ whereis meld meld: /usr/bin/meld /usr/lib/meld /usr/share/meld /usr/share/man/man1/meld.1.gz Is there any way to change the install location. Lets say if I want to install it in /usr/local/ can I do it using apt-get or aptitude? I know I can compile it from source and specify prefix option to configure script or make install but it would be better (and really easier) if I could do it using apt-get as I would be able to use uninstall, upgrade and other stuff that apt-get offers |
I just tried to install Crossover (Codeweavers) via the Ubuntu Software Center in Ubuntu 13.10 32-bit, but it didn't finish the installation. It just got stuck at about 90% (progress bar). After waiting approximately one hour, nothing happened. The installation was stuck, so I decided to restart the computer. The issue now is: Every time I try to reinstall Crossover via Software-Center, Ubuntu gives me a message box with the following error message: Package dependencies can not be resolved This error could be caused by required additional software packages which are missing or not installable. Furthermore there could be a conflict between software packages which are not allowed to be installed at the same time. The following packages have unmet dependencies crossover-trial: Depends: crossover-trial-bin (= 12.5.0-0ubuntu1 but 12.5.0-0ubuntu1 is not going to be installed) Any ideas about how to fix it? | Occasionally, when I'm installing stuff, I get an error like the following: Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages. How can I resolve this? |
I have found this on internet as a very interesting mathematical curiosity... If we have $x\in \mathbb{N}$, they say that if $x=\sum^{K}_{n=0}{(2n+1)}$, then $\sqrt{x}\in \mathbb{N}$ and $\sqrt{x}=K+1$. Is that always true? Why? This is my first question here! Thanks in advance and sorry for any mistakes. | I stumbled across this relationship while I was messing around. What's the proof, and how do I understand it intuitively? It doesn't really make sense to me that the sum of odd numbers up to $2x + 1$ should equal $x^2$. |
Are there any examples of such an argument? What would its premises be like? How could such an argument be possible? Where an argument is logically valid "if and only if it is not possible for all the premises to e true and the conclusion false." And logically false is defined as "if and only if it is not possible for the sentence to be true." (e.g. 'June will pass Chemistry 101 and she will not pass Chemistry 101'). | My text book gives the definition of validity as "An argument is valid IFF if the premises are true, then the conclusion must be true". Using a conditional elimination on the RHS of the IFF yields "An argument is valid IFF the premises are false or the conclusion is true". Yet, this seems strange to me. Am I doing something incorrect with my manipulation or is this definition actually true? Surely the criteria for a valid argument goes beyond a false set of premises or a true conclusion. |
I am using a plain JavaScript object. I have to create an exact copy of the object to make changes: var gRoll = {a:"pankaj",b: { a:"A",b:"c" }} var copy = gRoll; copy.a = "Karma"; This is making change in the parent object. Please give me solution to create copy of the object without referring to the old one. Same like prototype design pattern in OOPS. | What is the most efficient way to clone a JavaScript object? I've seen obj = eval(uneval(o)); being used, but . I've done things like obj = JSON.parse(JSON.stringify(o)); but question the efficiency. I've also seen recursive copying functions with various flaws. I'm surprised no canonical solution exists. |
I found this question some time ago in an Elementary Olympiad book: If $a, b, c, d$ are positive integers such that $abcd =1$, then prove that $(1+a)(1+b)(1+c)(1+d) \geq 16$. Evidently this was a direct consequence of Hölder's inequality, so I merely gave the following proof. $$(1^4+(a^{\frac{1}{4}})^4)(1^4+(b^{\frac{1}{4}})^4)(1^4+(c^{\frac{1}{4}})^4)(1^4+(d^{\frac{1}{4}})^4) \geq (1+(abcd)^{\frac{1}{4}})^4 $$ $$(1+a)(1+b)(1+c)(1+d) \geq (1+1)^4$$ $$(1+a)(1+b)(1+c)(1+d) \geq 16$$ QED. However, I was requested by my instructor to try the problem again using only the AM-GM inequality or the Cauchy-Schwarz inequality, because it is supposedly solvable using only those two. At this point I expanded the expression believing that all the terms so formed would be of the degree $4$, and would, when taken together in groups, yield a power of $abcd$ on the GM side, which could then be added. Doing so, however, I only get the weaker result that $(1+a)(1+b)(1+c)(1+d) \geq 14$. I would appreciate a hint for this tantalizing problem. | Suppose $a_1, a_2,\dots , a_n$ are $n$ positive real numbers with $a_1a_2 \dots a_n = 1$. Then what is the minimum value of $(1 + a_1)(1 + a_2). . .(1 + a_n)$ ? I think $(1 + a_1)(1 + a_2). . .(1 + a_n)$ takes its minimum value when $a_1=a_2=\dots=a_n=1$ and thus the minimum value is $2^n$. I don't know how to prove it. Please help. |
I have added two gifs in my code and I am trying to add text on top of it, but it ends up being on top or the bottom of the gif. How can I add something on top of a gif? I've tried adding text and positioning it on top of the gif using relative position and absolute but that does'nt work. HTML: <! DOCTYPE html> <html> <head> <meta charset="utf-8"> <link href="taniaWebsite11.css" type="text/css" rel="stylesheet"> <title> </title> </head> <body class="mainpage12"> <center> <img src="giphy1.gif"> <img src="1.gif"> </center> </body> </html> CSS: img{ height:1000px; width:1000px; } body.mainpage12{ background-color:black; } | I want to overlay one image with another using CSS. An example of this is the first image (the background if you like) will be a thumbnail link of a product, with the link opening a lightbox / popup showing a larger version of the image. On top of this linked image I would like an image of a magnifying glass, to show people that the image can be clicked to enlarge it (apparently this isn't obvious without the magnifying glass). |
While trying to benchmark as suggested when I asked question, I found that no matter what, whichever piece of code I tested second was dramatically longer by a factor of 1000 ns. I even swapped the pieces of code being tested to see if one really just was longer than the other, and the longer time swapped meaning it is placement in code that affects how long it runs. Here is my benchmark code: public class JavaAsmTest { public static void main(String [] args) { int numOfTrials = 10; long [] codeATimes = new long [numOfTrials]; long [] codeBTimes = new long [numOfTrials]; for(int trial = 0; trial < numOfTrials; trial++) { { long startTime; long endTime; long deltaTime; startTime = System.nanoTime(); for(int x = 0; x < 0x10000; x++) { for(int y = 0; y < 0x10000; y++) { codeB(x, y); //the code being tested }//end y loop }//end x loop endTime = System.nanoTime(); deltaTime = endTime - startTime; codeBTimes[trial] = deltaTime; }//end codeB Trial { long startTime; long endTime; long deltaTime; startTime = System.nanoTime(); for(int x = 0; x < 0x10000; x++) { for(int y = 0; y < 0x10000; y++) { codeA(x, y); //the other code being tested }//end y loop }//end x loop endTime = System.nanoTime(); deltaTime = endTime - startTime; codeATimes[trial] = deltaTime; }//end codeA Trial }//end trial loop long codeASum = 0; long codeBSum = 0; for(int x = 0; x < numOfTrials; x++) { codeASum += codeATimes[x]; codeBSum += codeBTimes[x]; } long codeAAvg = codeASum / numOfTrials; long codeBAvg = codeBSum / numOfTrials; System.out.println("codeA avg: " + codeAAvg); System.out.println("codeB avg: " + codeBAvg); }//end main private static void codeA(int a, int b) { int result = (a + b) & 0xFFFF; if(result == 0) { setZeroFlag(true); } else { setZeroFlag(false); } setSubtFlag(false); if((((a & 0x0FFF) + (b & 0x0FFF)) & 0x1000) != 0) { setHCarryFlag(true); } else { setHCarryFlag(false); } } private static void codeB(int a, int b) { int result = (a + b) & 0xFFFF; if(result == 0) { setZeroFlag(true); } else { setZeroFlag(false); } setSubtFlag(false); setHCarryFlag((((a & 0x0FFF) + (b & 0x0FFF)) & 0x1000) != 0); } private static void setZeroFlag(boolean flag) { } private static void setHCarryFlag(boolean flag) { } private static void setSubtFlag(boolean flag) { } } Please explain why this happens and how to prevent it to give me a realistic benchmark. | How do you write (and run) a correct micro-benchmark in Java? I'm looking for some code samples and comments illustrating various things to think about. Example: Should the benchmark measure time/iteration or iterations/time, and why? Related: |
I updated my 18.04 to 18.10 and after rebooting it gets stuck on the boot screen. What can I do to fix this? In case it helps, I have an Nvidia card... | I am trying to boot Ubuntu on my computer. When I boot Ubuntu, it boots to a black screen. How can I fix this? Table of Contents: |
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