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http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #Scheme | Scheme |
(import (scheme base)
(scheme inexact)
(scheme time)
(pstk))
(define PI 3.1415927)
;; Draws the hands on the canvas using the current time, and repeats each second
(define (hands canvas)
(canvas 'delete 'withtag "hands")
(let* ((time (current-second)) ; no time locality used, so displays time in GMT
(hours (floor (/ time 3600)))
(rem (- time (* hours 3600)))
(mins (floor (/ rem 60)))
(secs (- rem (* mins 60)))
(second-angle (* secs (* 2 PI 1/60)))
(minute-angle (* mins (* 2 PI 1/60)))
(hour-angle (* hours (* 2 PI 1/12))))
(canvas 'create 'line ; second hand
100 100
(+ 100 (* 90 (sin second-angle)))
(- 100 (* 90 (cos second-angle)))
'width: 1 'tags: "hands")
(canvas 'create 'line ; minute hand
100 100
(+ 100 (* 85 (sin minute-angle)))
(- 100 (* 85 (cos minute-angle)))
'width: 3
'capstyle: "projecting"
'tags: "hands")
(canvas 'create 'line ; hour hand
100 100
(+ 100 (* 60 (sin hour-angle)))
(- 100 (* 60 (cos hour-angle)))
'width: 7
'capstyle: "projecting"
'tags: "hands"))
(tk/after 1000 (lambda () (hands canvas))))
;; Create the initial frame, clock frame and hours
(let ((tk (tk-start)))
(tk/wm 'title tk "GMT Clock")
(let ((canvas (tk 'create-widget 'canvas)))
(tk/pack canvas)
(canvas 'configure 'height: 200 'width: 200)
(canvas 'create 'oval 2 2 198 198 'fill: "white" 'outline: "black")
(do ((h 1 (+ 1 h)))
((> h 12) )
(let ((angle (- (/ PI 2) (* h PI 1/6))))
(canvas 'create 'text
(+ 100 (* 90 (cos angle)))
(- 100 (* 90 (sin angle)))
'text: (number->string h)
'font: "{Helvetica -12}")))
(hands canvas))
(tk-event-loop tk))
|
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Erlang | Erlang | -module(srv).
-export([start/0, wait/0]).
start() ->
net_kernel:start([srv,shortnames]),
erlang:set_cookie(node(), rosetta),
Pid = spawn(srv,wait,[]),
register(srv,Pid),
io:fwrite("~p ready~n",[node(Pid)]),
ok.
wait() ->
receive
{echo, Pid, Any} ->
io:fwrite("-> ~p from ~p~n", [Any, node(Pid)]),
Pid ! {hello, Any},
wait();
Any -> io:fwrite("Error ~p~n", [Any])
end. |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #CoffeeScript | CoffeeScript |
# runs under node.js
dns = require 'dns'
dns.resolve4 'www.kame.net', (err, addresses) ->
console.log 'IP4'
console.log addresses
dns.resolve6 'www.kame.net', (err, addresses) ->
console.log 'IP6'
console.log addresses
|
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Common_Lisp | Common Lisp | (sb-bsd-sockets:host-ent-addresses
(sb-bsd-sockets:get-host-by-name "www.rosettacode.org"))
(#(71 19 147 227)) |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Crystal | Crystal | require "socket"
Socket::Addrinfo.resolve(
"www.kame.net",
80,
type: Socket::Type::STREAM
).each { |a|
puts a.ip_address.address
} |
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #Openscad | Openscad | level = 8;
linewidth = .1; // fraction of segment length
sqrt2 = pow(2, .5);
// Draw a dragon curve "level" going from [0,0] to [1,0]
module dragon(level) {
if (level <= 0) {
translate([.5,0]) cube([1+linewidth,linewidth,linewidth],center=true);
} else {
rotate(-45) scale(1/sqrt2) dragon(level-1);
translate([1,0]) rotate(-135) scale(1/sqrt2) dragon(level-1);
}
}
scale(40) { // scale to nicely visible in the default GUI
sphere(1.5*linewidth / pow(2,level/2)); // mark the start of the curve
dragon(level);
}
|
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #Elixir | Elixir | defmodule Linear_combination do
def display(coeff) do
Enum.with_index(coeff)
|> Enum.map_join(fn {n,i} ->
{m,s} = if n<0, do: {-n,"-"}, else: {n,"+"}
case {m,i} do
{0,_} -> ""
{1,i} -> "#{s}e(#{i+1})"
{n,i} -> "#{s}#{n}*e(#{i+1})"
end
end)
|> String.trim_leading("+")
|> case do
"" -> IO.puts "0"
str -> IO.puts str
end
end
end
coeffs =
[ [1, 2, 3],
[0, 1, 2, 3],
[1, 0, 3, 4],
[1, 2, 0],
[0, 0, 0],
[0],
[1, 1, 1],
[-1, -1, -1],
[-1, -2, 0, -3],
[-1]
]
Enum.each(coeffs, &Linear_combination.display(&1)) |
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #F.23 | F# |
// Display a linear combination. Nigel Galloway: March 28th., 2018
let fN g =
let rec fG n g=match g with
|0::g -> fG (n+1) g
|1::g -> printf "+e(%d)" n; fG (n+1) g
|(-1)::g -> printf "-e(%d)" n; fG (n+1) g
|i::g -> printf "%+de(%d)" i n; fG (n+1) g
|_ -> printfn ""
let rec fN n g=match g with
|0::g -> fN (n+1) g
|1::g -> printf "e(%d)" n; fG (n+1) g
|(-1)::g -> printf "-e(%d)" n; fG (n+1) g
|i::g -> printf "%de(%d)" i n; fG (n+1) g
|_ -> printfn "0"
fN 1 g
|
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Factor | Factor | def class Foo {
"""
This is a docstring. Every object in Fancy can have it's own docstring.
Either defined in the source code, like this one, or by using the Object#docstring: method
"""
def a_method {
"""
Same for methods. They can have docstrings, too.
"""
}
}
Foo docstring println # prints docstring Foo class
Foo instance_method: 'a_method . docstring println # prints method's docstring |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Fancy | Fancy | def class Foo {
"""
This is a docstring. Every object in Fancy can have it's own docstring.
Either defined in the source code, like this one, or by using the Object#docstring: method
"""
def a_method {
"""
Same for methods. They can have docstrings, too.
"""
}
}
Foo docstring println # prints docstring Foo class
Foo instance_method: 'a_method . docstring println # prints method's docstring |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Forth | Forth | \ this is a comment |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #Go | Go | package main
import "fmt"
func averageSquareDiff(f float64, preds []float64) (av float64) {
for _, pred := range preds {
av += (pred - f) * (pred - f)
}
av /= float64(len(preds))
return
}
func diversityTheorem(truth float64, preds []float64) (float64, float64, float64) {
av := 0.0
for _, pred := range preds {
av += pred
}
av /= float64(len(preds))
avErr := averageSquareDiff(truth, preds)
crowdErr := (truth - av) * (truth - av)
div := averageSquareDiff(av, preds)
return avErr, crowdErr, div
}
func main() {
predsArray := [2][]float64{{48, 47, 51}, {48, 47, 51, 42}}
truth := 49.0
for _, preds := range predsArray {
avErr, crowdErr, div := diversityTheorem(truth, preds)
fmt.Printf("Average-error : %6.3f\n", avErr)
fmt.Printf("Crowd-error : %6.3f\n", crowdErr)
fmt.Printf("Diversity : %6.3f\n\n", div)
}
} |
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #Sidef | Sidef | func normalize (vec) { vec »/» (vec »*« vec -> sum.sqrt) }
func dot (x, y) { -(x »*« y -> sum) `max` 0 }
var x = var y = 255
x += 1 if x.is_even # must be odd
var light = normalize([ 3, 2, -5 ])
var depth = 255
func draw_sphere(rad, k, ambient) {
var pixels = []
var r2 = (rad * rad)
var range = (-rad .. rad)
for x,y in (range ~X range) {
if ((var x2 = x*x) + (var y2 = y*y) < r2) {
var vector = normalize([x, y, (r2 - x2 - y2).sqrt])
var intensity = (dot(light, vector)**k + ambient)
var pixel = (0 `max` (intensity*depth -> int) `min` depth)
pixels << pixel
}
else {
pixels << 0
}
}
return pixels
}
var outfile = %f'sphere-sidef.pgm'
var out = outfile.open('>:raw')
out.say("P5\n#{x} #{y}\n#{depth}") # .pgm header
out.print(draw_sphere((x-1)/2, .9, .2).map{.chr}.join)
out.close |
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #J | J | depth=: (i.~ ~.)@(0 i."1~' '=];._2)
tree=: (i: 0>.<:@{:)\
width=: {{NB. y is tree
c=. *i.#y NB. children
NB. sum of children, inductively
y (+//. c&*)`(~.@[)`]}^:_ c
}}
NB. avoid dark colors
NB. avoid dark colors
NB. avoid dark colors
pastel=: {{256#.192+?y$,:3#64}}
task=: {{
depths=: depth y NB. outline structure
t=: tree depths NB. outline as tree
pad=: (i.#depths) -. t,I.(=>./)depths
tr=: t,pad NB. outline as constant depth tree
dr=: depths,1+pad{depths
lines=:(#dr){.<@dlb;._2 y
widths=. width tr NB. column widths
top=. I.2>dr
color=.<"1 hfd 8421504 (I.tr e.pad)} (top top} tr)&{^:_ (<:2^24),pastel<:#dr
r=.'{| class="wikitable" style="text-align: center;"',LF
for_d.~.dr do. NB. descend through the depths
k=.I.d=dr NB. all lines at this depth
p=. |:({:,~{&tr)^:d ,:k
j=. k/:p NB. order padding to fit parents
r=. r,'|-',LF
r=. r,;'| style="background: #',L:0 (j{color),L:0'" colspan=',L:0(j{widths),&":each' | ',L:0 (j{lines),L:0 LF
end.
r=.r,'|}',LF
}} |
http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #Scratch | Scratch | $ include "seed7_05.s7i";
include "float.s7i";
include "math.s7i";
include "draw.s7i";
include "keybd.s7i";
include "time.s7i";
include "duration.s7i";
const integer: WINDOW_WIDTH is 200;
const integer: WINDOW_HEIGHT is 200;
const color: BACKGROUND is White;
const color: FOREGROUND is Black;
const color: CLOCKCOLOR is Aqua;
const proc: main is func
local
var char: command is ' ';
var time: start_time is time.value;
var float: alpha is 0.0;
var integer: x is 0;
begin
screen(WINDOW_WIDTH, WINDOW_HEIGHT);
clear(curr_win, BACKGROUND);
KEYBOARD := GRAPH_KEYBOARD;
command := busy_getc(KEYBOARD);
while command <> 'q' do
start_time := truncToSecond(time(NOW));
clear(curr_win, BACKGROUND);
fcircle(100, 100, 95, CLOCKCOLOR);
circle(100, 100, 95, FOREGROUND);
for x range 0 to 60 do
alpha := flt(x-15) * PI / 30.0;
if x mod 5 = 0 then
lineTo(100 + round(cos(alpha)*95.0),
100 + round(sin(alpha)*95.0),
100 + round(cos(alpha)*85.0),
100 + round(sin(alpha)*85.0), FOREGROUND);
else
lineTo(100 + round(cos(alpha)*95.0),
100 + round(sin(alpha)*95.0),
100 + round(cos(alpha)*92.0),
100 + round(sin(alpha)*92.0), FOREGROUND);
end if;
end for;
alpha := flt(start_time.second-15) * PI / 30.0;
lineTo(100, 100, 100 + round(cos(alpha)*85.0), 100 + round(sin(alpha)*85.0), FOREGROUND);
alpha := flt(start_time.minute-15) * PI / 30.0;
lineTo(100 + round(cos(alpha-PI/2.0)*5.0),
100 + round(sin(alpha-PI/2.0)*5.0),
100 + round(cos(alpha)*75.0),
100 + round(sin(alpha)*75.0), FOREGROUND);
lineTo(100 + round(cos(alpha+PI/2.0)*5.0),
100 + round(sin(alpha+PI/2.0)*5.0),
100 + round(cos(alpha)*75.0),
100 + round(sin(alpha)*75.0), FOREGROUND);
alpha := (flt(start_time.hour)+flt(start_time.minute)/60.0-3.0) * PI / 6.0;
lineTo(100 + round(cos(alpha-PI/2.0)*7.0),
100 + round(sin(alpha-PI/2.0)*7.0),
100 + round(cos(alpha)*50.0),
100 + round(sin(alpha)*50.0), FOREGROUND);
lineTo(100 + round(cos(alpha+PI/2.0)*7.0),
100 + round(sin(alpha+PI/2.0)*7.0),
100 + round(cos(alpha)*50.0),
100 + round(sin(alpha)*50.0), FOREGROUND);
fcircle(100, 100, 7, CLOCKCOLOR);
circle(100, 100, 7, FOREGROUND);
DRAW_FLUSH;
await(start_time + 1 . SECONDS);
command := busy_getc(KEYBOARD);
end while;
end func; |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Factor | Factor | USING: concurrency.distributed concurrency.messaging threads io.sockets io.servers ;
QUALIFIED: concurrency.messaging
: prettyprint-message ( -- ) concurrency.messaging:receive . flush prettyprint-message ;
[ prettyprint-message ] "logger" spawn dup name>> register-remote-thread
"127.0.0.1" 9000 <inet4> <node-server> start-server |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Go | Go | package main
import (
"errors"
"log"
"net"
"net/http"
"net/rpc"
)
type TaxComputer float64
func (taxRate TaxComputer) Tax(x float64, r *float64) error {
if x < 0 {
return errors.New("Negative values not allowed")
}
*r = x * float64(taxRate)
return nil
}
func main() {
c := TaxComputer(.05)
rpc.Register(c)
rpc.HandleHTTP()
listener, err := net.Listen("tcp", ":1234")
if err != nil {
log.Fatal(err)
}
http.Serve(listener, nil)
} |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #D | D | import std.stdio, std.socket;
void main() {
auto domain = "www.kame.net", port = "80";
auto a = getAddressInfo(domain, port, AddressFamily.INET);
writefln("IPv4 address for %s: %s", domain, a[0].address);
a = getAddressInfo(domain, port, AddressFamily.INET6);
writefln("IPv6 address for %s: %s", domain, a[0].address);
} |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Delphi | Delphi | program DNSQuerying;
{$APPTYPE CONSOLE}
uses
IdGlobal, IdStackWindows;
const
DOMAIN_NAME = 'www.kame.net';
var
lStack: TIdStackWindows;
begin
lStack := TIdStackWindows.Create;
try
Writeln(DOMAIN_NAME);
Writeln('IPv4: ' + lStack.ResolveHost(DOMAIN_NAME));
Writeln('IPv6: ' + lStack.ResolveHost(DOMAIN_NAME, Id_IPv6));
finally
lStack.Free;
end;
end. |
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #PARI.2FGP | PARI/GP | level = 13
p = [0, 1]; \\ complex number points, initially 0 to 1
\\ "unfold" at the current endpoint p[#p].
\\ p[^-1] so as not to duplicate that endpoint.
\\
\\ * end
\\ --> |
\\ / |
\\ v
\\ *------->*
\\ 0,0 p[#p]
\\
for(i=1,level, my(end = (1+I)*p[#p]); \
p = concat(p, apply(z->(end - I*z), Vecrev(p[^-1]))))
plothraw(apply(real,p),apply(imag,p), 1); \\ flag=1 join points |
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #Factor | Factor | USING: formatting kernel match math pair-rocket regexp sequences ;
MATCH-VARS: ?a ?b ;
: choose-term ( coeff i -- str )
1 + { } 2sequence {
{ 0 _ } => [ "" ]
{ 1 ?a } => [ ?a "e(%d)" sprintf ]
{ -1 ?a } => [ ?a "-e(%d)" sprintf ]
{ ?a ?b } => [ ?a ?b "%d*e(%d)" sprintf ]
} match-cond ;
: linear-combo ( seq -- str )
[ choose-term ] map-index harvest " + " join
R/ \+ -/ "- " re-replace [ "0" ] when-empty ;
{ { 1 2 3 } { 0 1 2 3 } { 1 0 3 4 } { 1 2 0 } { 0 0 0 } { 0 }
{ 1 1 1 } { -1 -1 -1 } { -1 -2 0 -3 } { -1 } }
[ dup linear-combo "%-14u -> %s\n" printf ] each |
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #FreeBASIC | FreeBASIC | Dim scalars(1 To 10, 1 To 4) As Integer => {{1, 2, 3}, {0, 1, 2, 3}, _
{1, 0, 3, 4}, {1, 2, 0}, {0, 0, 0}, {0}, {1, 1, 1}, {-1, -1, -1}, _
{-1, -2, 0, -3}, {-1}}
For n As Integer = 1 To Ubound(scalars)
Dim As String cadena = ""
Dim As Integer scalar
For m As Integer = 1 To Ubound(scalars,2)
scalar = scalars(n, m)
If scalar <> 0 Then
If scalar = 1 Then
cadena &= "+e" & m
Elseif scalar = -1 Then
cadena &= "-e" & m
Else
If scalar > 0 Then
cadena &= Chr(43) & scalar & "*e" & m
Else
cadena &= scalar & "*e" & m
End If
End If
End If
Next m
If cadena = "" Then cadena = "0"
If Left(cadena, 1) = "+" Then cadena = Right(cadena, Len(cadena)-1)
Print cadena
Next n
Sleep |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Fortran | Fortran | SUBROUTINE SHOW(A,N) !Prints details to I/O unit LINPR.
REAL*8 A !Distance to the next node.
INTEGER N !Number of the current node. |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #FreeBASIC | FreeBASIC | // Example serves as an example but does nothing useful.
//
// A package comment preceeds the package clause and explains the purpose
// of the package.
package example
// Exported variables.
var (
// lookie
X, Y, Z int // popular names
)
/* XP does nothing.
Here's a block comment. */
func XP() { // here we go!
// comments inside
}
// Non-exported.
func nonXP() {}
// Doc not extracted.
var MEMEME int |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Go | Go | // Example serves as an example but does nothing useful.
//
// A package comment preceeds the package clause and explains the purpose
// of the package.
package example
// Exported variables.
var (
// lookie
X, Y, Z int // popular names
)
/* XP does nothing.
Here's a block comment. */
func XP() { // here we go!
// comments inside
}
// Non-exported.
func nonXP() {}
// Doc not extracted.
var MEMEME int |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #Groovy | Groovy | class DiversityPredictionTheorem {
private static double square(double d) {
return d * d
}
private static double averageSquareDiff(double d, double[] predictions) {
return Arrays.stream(predictions)
.map({ it -> square(it - d) })
.average()
.orElseThrow()
}
private static String diversityTheorem(double truth, double[] predictions) {
double average = Arrays.stream(predictions)
.average()
.orElseThrow()
return String.format("average-error : %6.3f%n", averageSquareDiff(truth, predictions)) + String.format("crowd-error : %6.3f%n", square(truth - average)) + String.format("diversity : %6.3f%n", averageSquareDiff(average, predictions))
}
static void main(String[] args) {
println(diversityTheorem(49.0, [48.0, 47.0, 51.0] as double[]))
println(diversityTheorem(49.0, [48.0, 47.0, 51.0, 42.0] as double[]))
}
} |
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #Smalltalk | Smalltalk |
Point3D :=
Point subclass:#Point3D
instanceVariableNames:'z'
classVariableNames:''
poolDictionaries:''
category:''
inEnvironment:nil.
Point3D compile:'z ^ z'.
Point3D compile:'z:v z := v'.
normalize := [:v | |invLen|
invLen := 1 / (dot value:v value:v) sqrt.
v x: v x * invLen.
v y: v y * invLen.
v z: v z * invLen.
].
dot := [:a :b |
(a x * b x) + (a y * b y) + (a z * b z)
].
drawSphere := [:r :k :amb :dir |
|w h imh vec img|
w := r*4. h := r*3.
img := Image width:w height:h depth:8.
img photometric:#blackIs0; createPixelStore.
vec := Point3D new.
0-r to:r do:[:x |
0-r to:r do:[:y |
|z s lum|
(z := (r*r) - (x*x) - (y*y)) >= 0 ifTrue:[
vec x: x.
vec y: y.
vec z: z sqrt.
normalize value:vec.
s := dot value:dir value:vec.
s < 0 ifTrue:[ s := 0 ].
lum := 255 * ((s raisedTo: k) + amb) / (1 + amb).
lum < 0 ifTrue:[
lum := 0
] ifFalse:[ lum > 255 ifTrue:[
lum := 255
]].
img atX:(x+(w//2)) y:(y+(h//2)) put:(Color greyByte:lum).
]
]
].
img
].
main := [
|dir img|
dir := Point3D new x:-30; y:-30; z:50; yourself.
normalize value:dir.
img := drawSphere value: 100 value: 1.5 value: 0.2 value: dir.
img displayOn:(View new extent:400@400; openAndWait).
img saveOn:'sphere.png'.
].
main value.
|
http://rosettacode.org/wiki/Doubly-linked_list/Definition | Doubly-linked list/Definition | Define the data structure for a complete Doubly Linked List.
The structure should support adding elements to the head, tail and middle of the list.
The structure should not allow circular loops
See also
Array
Associative array: Creation, Iteration
Collections
Compound data type
Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
Linked list
Queue: Definition, Usage
Set
Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
Stack
| #Action.21 | Action! | SET EndProg=* |
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #JavaScript | JavaScript | (() => {
"use strict";
// ----------- NESTED TABLES FROM OUTLINE ------------
// wikiTablesFromOutline :: [String] -> String -> String
const wikiTablesFromOutline = colorSwatch =>
outline => forestFromIndentedLines(
indentLevelsFromLines(lines(outline))
)
.map(wikiTableFromTree(colorSwatch))
.join("\n\n");
// wikiTableFromTree :: [String] -> Tree String -> String
const wikiTableFromTree = colorSwatch =>
compose(
wikiTableFromRows,
levels,
paintedTree(colorSwatch),
widthLabelledTree,
ap(paddedTree(""))(treeDepth)
);
// ---------------------- TEST -----------------------
// main :: IO ()
const main = () => {
const outline = `Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.`;
return wikiTablesFromOutline([
"#ffffe6",
"#ffebd2",
"#f0fff0",
"#e6ffff",
"#ffeeff"
])(outline);
};
// --------- TREE STRUCTURE FROM NESTED TEXT ---------
// forestFromIndentedLines :: [(Int, String)] ->
// [Tree String]
const forestFromIndentedLines = tuples => {
const go = xs =>
0 < xs.length ? (() => {
// First line and its sub-tree,
const [indented, body] = Array.from(
xs[0]
),
[tree, rest] = Array.from(
span(compose(lt(indented), fst))(
tail(xs)
)
);
// followed by the rest.
return [
Node(body)(go(tree))
].concat(go(rest));
})() : [];
return go(tuples);
};
// indentLevelsFromLines :: [String] -> [(Int, String)]
const indentLevelsFromLines = xs => {
const
pairs = xs.map(
x => bimap(length)(cs => cs.join(""))(
span(isSpace)(list(x))
)
),
indentUnit = pairs.reduce(
(a, tpl) => {
const i = tpl[0];
return 0 < i ? (
i < a ? i : a
) : a;
},
Infinity
);
return [Infinity, 0].includes(indentUnit) ? (
pairs
) : pairs.map(first(n => n / indentUnit));
};
// ------------ TREE PADDED TO EVEN DEPTH ------------
// paddedTree :: a -> Tree a -> Int -> Tree a
const paddedTree = padValue =>
// All descendants expanded to same depth
// with empty nodes where needed.
node => depth => {
const go = n => tree =>
1 < n ? (() => {
const children = nest(tree);
return Node(root(tree))(
(
0 < children.length ? (
children
) : [Node(padValue)([])]
).map(go(n - 1))
);
})() : tree;
return go(depth)(node);
};
// treeDepth :: Tree a -> Int
const treeDepth = tree =>
foldTree(
() => xs => 0 < xs.length ? (
1 + maximum(xs)
) : 1
)(tree);
// ------------- SUBTREE WIDTHS MEASURED -------------
// widthLabelledTree :: Tree a -> Tree (a, Int)
const widthLabelledTree = tree =>
// A tree in which each node is labelled with
// the width of its own subtree.
foldTree(x => xs =>
0 < xs.length ? (
Node(Tuple(x)(
xs.reduce(
(a, node) => a + snd(root(node)),
0
)
))(xs)
) : Node(Tuple(x)(1))([])
)(tree);
// -------------- COLOR SWATCH APPLIED ---------------
// paintedTree :: [String] -> Tree a -> Tree (String, a)
const paintedTree = colorSwatch =>
tree => 0 < colorSwatch.length ? (
Node(
Tuple(colorSwatch[0])(root(tree))
)(
zipWith(compose(fmapTree, Tuple))(
cycle(colorSwatch.slice(1))
)(
nest(tree)
)
)
) : fmapTree(Tuple(""))(tree);
// --------------- WIKITABLE RENDERED ----------------
// wikiTableFromRows ::
// [[(String, (String, Int))]] -> String
const wikiTableFromRows = rows => {
const
cw = color => width => {
const go = w =>
1 < w ? (
`colspan=${w} `
) : "";
return `style="background:${color}; "` + (
` ${go(width)}`
);
},
cellText = ctw => {
const [color, tw] = Array.from(ctw);
const [txt, width] = Array.from(tw);
return 0 < txt.length ? (
`| ${cw(color)(width)}| ${txt}`
) : "| |";
},
classText = "class=\"wikitable\"",
styleText = "style=\"text-align:center;\"",
header = `{| ${classText} ${styleText}\n|-`,
tableBody = rows.map(
cells => cells.map(cellText).join("\n")
).join("\n|-\n");
return `${header}\n${tableBody}\n|}`;
};
// ------------------ GENERIC TREES ------------------
// Node :: a -> [Tree a] -> Tree a
const Node = v =>
// Constructor for a Tree node which connects a
// value of some kind to a list of zero or
// more child trees.
xs => ({
type: "Node",
root: v,
nest: xs || []
});
// fmapTree :: (a -> b) -> Tree a -> Tree b
const fmapTree = f => {
// A new tree. The result of a
// structure-preserving application of f
// to each root in the existing tree.
const go = t => Node(
f(t.root)
)(
t.nest.map(go)
);
return go;
};
// foldTree :: (a -> [b] -> b) -> Tree a -> b
const foldTree = f => {
// The catamorphism on trees. A summary
// value obtained by a depth-first fold.
const go = tree => f(
root(tree)
)(
nest(tree).map(go)
);
return go;
};
// levels :: Tree a -> [[a]]
const levels = tree => {
// A list of lists, grouping the root
// values of each level of the tree.
const go = (a, node) => {
const [h, ...t] = 0 < a.length ? (
a
) : [
[],
[]
];
return [
[node.root, ...h],
...node.nest.slice(0)
.reverse()
.reduce(go, t)
];
};
return go([], tree);
};
// nest :: Tree a -> [a]
const nest = tree => {
// Allowing for lazy (on-demand) evaluation.
// If the nest turns out to be a function –
// rather than a list – that function is applied
// here to the root, and returns a list.
const xs = tree.nest;
return "function" !== typeof xs ? (
xs
) : xs(root(tree));
};
// root :: Tree a -> a
const root = tree =>
// The value attached to a tree node.
tree.root;
// --------------------- GENERIC ---------------------
// Just :: a -> Maybe a
const Just = x => ({
type: "Maybe",
Nothing: false,
Just: x
});
// Nothing :: Maybe a
const Nothing = () => ({
type: "Maybe",
Nothing: true
});
// Tuple (,) :: a -> b -> (a, b)
const Tuple = a =>
b => ({
type: "Tuple",
"0": a,
"1": b,
length: 2
});
// apFn :: (a -> b -> c) -> (a -> b) -> (a -> c)
const ap = f =>
// Applicative instance for functions.
// f(x) applied to g(x).
g => x => f(x)(
g(x)
);
// bimap :: (a -> b) -> (c -> d) -> (a, c) -> (b, d)
const bimap = f =>
// Tuple instance of bimap.
// A tuple of the application of f and g to the
// first and second values respectively.
g => tpl => Tuple(f(tpl[0]))(
g(tpl[1])
);
// compose (<<<) :: (b -> c) -> (a -> b) -> a -> c
const compose = (...fs) =>
// A function defined by the right-to-left
// composition of all the functions in fs.
fs.reduce(
(f, g) => x => f(g(x)),
x => x
);
// cycle :: [a] -> Generator [a]
const cycle = function* (xs) {
// An infinite repetition of xs,
// from which an arbitrary prefix
// may be taken.
const lng = xs.length;
let i = 0;
while (true) {
yield xs[i];
i = (1 + i) % lng;
}
};
// first :: (a -> b) -> ((a, c) -> (b, c))
const first = f =>
// A simple function lifted to one which applies
// to a tuple, transforming only its first item.
xy => {
const tpl = Tuple(f(xy[0]))(xy[1]);
return Array.isArray(xy) ? (
Array.from(tpl)
) : tpl;
};
// fst :: (a, b) -> a
const fst = tpl =>
// First member of a pair.
tpl[0];
// isSpace :: Char -> Bool
const isSpace = c =>
// True if c is a white space character.
(/\s/u).test(c);
// length :: [a] -> Int
const length = xs =>
// Returns Infinity over objects without finite
// length. This enables zip and zipWith to choose
// the shorter argument when one is non-finite,
// like cycle, repeat etc
"GeneratorFunction" !== xs.constructor
.constructor.name ? (
xs.length
) : Infinity;
// lines :: String -> [String]
const lines = s =>
// A list of strings derived from a single
// string delimited by newline and or CR.
0 < s.length ? (
s.split(/[\r\n]+/u)
) : [];
// list :: StringOrArrayLike b => b -> [a]
const list = xs =>
// xs itself, if it is an Array,
// or an Array derived from xs.
Array.isArray(xs) ? (
xs
) : Array.from(xs || []);
// lt (<) :: Ord a => a -> a -> Bool
const lt = a =>
b => a < b;
// maximum :: Ord a => [a] -> a
const maximum = xs => (
// The largest value in a non-empty list.
ys => 0 < ys.length ? (
ys.slice(1).reduce(
(a, y) => y > a ? (
y
) : a, ys[0]
)
) : undefined
)(list(xs));
// snd :: (a, b) -> b
const snd = tpl =>
// Second member of a pair.
tpl[1];
// span :: (a -> Bool) -> [a] -> ([a], [a])
const span = p =>
// Longest prefix of xs consisting of elements which
// all satisfy p, tupled with the remainder of xs.
xs => {
const i = xs.findIndex(x => !p(x));
return -1 !== i ? (
Tuple(xs.slice(0, i))(
xs.slice(i)
)
) : Tuple(xs)([]);
};
// tail :: [a] -> [a]
const tail = xs =>
// A new list consisting of all
// items of xs except the first.
"GeneratorFunction" !== xs.constructor
.constructor.name ? (
(ys => 0 < ys.length ? ys.slice(1) : [])(
xs
)
) : (take(1)(xs), xs);
// take :: Int -> [a] -> [a]
// take :: Int -> String -> String
const take = n =>
// The first n elements of a list,
// string of characters, or stream.
xs => "GeneratorFunction" !== xs
.constructor.constructor.name ? (
xs.slice(0, n)
) : [].concat(...Array.from({
length: n
}, () => {
const x = xs.next();
return x.done ? [] : [x.value];
}));
// uncons :: [a] -> Maybe (a, [a])
const uncons = xs => {
// Just a tuple of the head of xs and its tail,
// Or Nothing if xs is an empty list.
const lng = length(xs);
return (0 < lng) ? (
Infinity > lng ? (
// Finite list
Just(Tuple(xs[0])(xs.slice(1)))
) : (() => {
// Lazy generator
const nxt = take(1)(xs);
return 0 < nxt.length ? (
Just(Tuple(nxt[0])(xs))
) : Nothing();
})()
) : Nothing();
};
// zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
const zipWith = f =>
// A list with the length of the shorter of
// xs and ys, defined by zipping with a
// custom function, rather than with the
// default tuple constructor.
xs => ys => {
const n = Math.min(length(xs), length(ys));
return Infinity > n ? (
(([as, bs]) => Array.from({
length: n
}, (_, i) => f(as[i])(
bs[i]
)))([xs, ys].map(
take(n)
))
) : zipWithGen(f)(xs)(ys);
};
// zipWithGen :: (a -> b -> c) ->
// Gen [a] -> Gen [b] -> Gen [c]
const zipWithGen = f => ga => gb => {
const go = function* (ma, mb) {
let
a = ma,
b = mb;
while (!a.Nothing && !b.Nothing) {
const
ta = a.Just,
tb = b.Just;
yield f(fst(ta))(fst(tb));
a = uncons(snd(ta));
b = uncons(snd(tb));
}
};
return go(uncons(ga), uncons(gb));
};
// MAIN ---
return main();
})(); |
http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #Seed7 | Seed7 | $ include "seed7_05.s7i";
include "float.s7i";
include "math.s7i";
include "draw.s7i";
include "keybd.s7i";
include "time.s7i";
include "duration.s7i";
const integer: WINDOW_WIDTH is 200;
const integer: WINDOW_HEIGHT is 200;
const color: BACKGROUND is White;
const color: FOREGROUND is Black;
const color: CLOCKCOLOR is Aqua;
const proc: main is func
local
var char: command is ' ';
var time: start_time is time.value;
var float: alpha is 0.0;
var integer: x is 0;
begin
screen(WINDOW_WIDTH, WINDOW_HEIGHT);
clear(curr_win, BACKGROUND);
KEYBOARD := GRAPH_KEYBOARD;
command := busy_getc(KEYBOARD);
while command <> 'q' do
start_time := truncToSecond(time(NOW));
clear(curr_win, BACKGROUND);
fcircle(100, 100, 95, CLOCKCOLOR);
circle(100, 100, 95, FOREGROUND);
for x range 0 to 60 do
alpha := flt(x-15) * PI / 30.0;
if x mod 5 = 0 then
lineTo(100 + round(cos(alpha)*95.0),
100 + round(sin(alpha)*95.0),
100 + round(cos(alpha)*85.0),
100 + round(sin(alpha)*85.0), FOREGROUND);
else
lineTo(100 + round(cos(alpha)*95.0),
100 + round(sin(alpha)*95.0),
100 + round(cos(alpha)*92.0),
100 + round(sin(alpha)*92.0), FOREGROUND);
end if;
end for;
alpha := flt(start_time.second-15) * PI / 30.0;
lineTo(100, 100, 100 + round(cos(alpha)*85.0), 100 + round(sin(alpha)*85.0), FOREGROUND);
alpha := flt(start_time.minute-15) * PI / 30.0;
lineTo(100 + round(cos(alpha-PI/2.0)*5.0),
100 + round(sin(alpha-PI/2.0)*5.0),
100 + round(cos(alpha)*75.0),
100 + round(sin(alpha)*75.0), FOREGROUND);
lineTo(100 + round(cos(alpha+PI/2.0)*5.0),
100 + round(sin(alpha+PI/2.0)*5.0),
100 + round(cos(alpha)*75.0),
100 + round(sin(alpha)*75.0), FOREGROUND);
alpha := (flt(start_time.hour)+flt(start_time.minute)/60.0-3.0) * PI / 6.0;
lineTo(100 + round(cos(alpha-PI/2.0)*7.0),
100 + round(sin(alpha-PI/2.0)*7.0),
100 + round(cos(alpha)*50.0),
100 + round(sin(alpha)*50.0), FOREGROUND);
lineTo(100 + round(cos(alpha+PI/2.0)*7.0),
100 + round(sin(alpha+PI/2.0)*7.0),
100 + round(cos(alpha)*50.0),
100 + round(sin(alpha)*50.0), FOREGROUND);
fcircle(100, 100, 7, CLOCKCOLOR);
circle(100, 100, 7, FOREGROUND);
DRAW_FLUSH;
await(start_time + 1 . SECONDS);
command := busy_getc(KEYBOARD);
end while;
end func; |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Haskell | Haskell | var net = require('net')
var server = net.createServer(function (c){
c.write('hello\r\n')
c.pipe(c) // echo messages back
})
server.listen(3000, 'localhost')
|
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #JavaScript | JavaScript | var net = require('net')
var server = net.createServer(function (c){
c.write('hello\r\n')
c.pipe(c) // echo messages back
})
server.listen(3000, 'localhost')
|
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Erlang | Erlang |
33> {ok, {hostent, Host, Aliases, AddrType, Bytes, AddrList}} = inet:gethostbyname("www.kame.net", inet).
{ok,{hostent,"orange.kame.net",
["www.kame.net"],
inet,4,
[{203,178,141,194}]}}
34> [inet_parse:ntoa(Addr) || Addr <- AddrList].
["203.178.141.194"]
35> f().
ok
36> {ok, {hostent, Host, Aliases, AddrType, Bytes, AddrList}} = inet:gethostbyname("www.kame.net", inet6).
{ok,{hostent,"orange.kame.net",[],inet6,16,
[{8193,512,3583,65521,534,16127,65201,17623}]}}
37> [inet_parse:ntoa(Addr) || Addr <- AddrList].
["2001:200:DFF:FFF1:216:3EFF:FEB1:44D7"]
|
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #Pascal | Pascal | procedure dcr(step,dir:integer;length:real);
begin;
step:=step -1;
length:= length/sqrt(2);
if dir > 0 then
begin
if step > 0 then
begin
turnright(45);
dcr(step,1,length);
turnleft(90);
dcr(step,0,length);
turnright(45);
end
else
begin
turnright(45);
forward(length);
turnleft(90);
forward(length);
turnright(45);
end;
end
else
begin
if step > 0 then
begin
turnleft(45);
dcr(step,1,length);
turnright(90);
dcr(step,0,length);
turnleft(45);
end
else
begin
turnleft(45);
forward(length);
turnright(90);
forward(length);
turnleft(45);
end;
end;
end; |
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #Go | Go | package main
import (
"fmt"
"strings"
)
func linearCombo(c []int) string {
var sb strings.Builder
for i, n := range c {
if n == 0 {
continue
}
var op string
switch {
case n < 0 && sb.Len() == 0:
op = "-"
case n < 0:
op = " - "
case n > 0 && sb.Len() == 0:
op = ""
default:
op = " + "
}
av := n
if av < 0 {
av = -av
}
coeff := fmt.Sprintf("%d*", av)
if av == 1 {
coeff = ""
}
sb.WriteString(fmt.Sprintf("%s%se(%d)", op, coeff, i+1))
}
if sb.Len() == 0 {
return "0"
} else {
return sb.String()
}
}
func main() {
combos := [][]int{
{1, 2, 3},
{0, 1, 2, 3},
{1, 0, 3, 4},
{1, 2, 0},
{0, 0, 0},
{0},
{1, 1, 1},
{-1, -1, -1},
{-1, -2, 0, -3},
{-1},
}
for _, c := range combos {
t := strings.Replace(fmt.Sprint(c), " ", ", ", -1)
fmt.Printf("%-15s -> %s\n", t, linearCombo(c))
}
} |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Gri | Gri | `My Hello Message'
Print a greeting to the user.
This is only a short greeting.
{
show "hello"
} |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Haskell | Haskell | -- |This is a documentation comment for the following function
square1 :: Int -> Int
square1 x = x * x
-- |It can even
-- span multiple lines
square2 :: Int -> Int
square2 x = x * x
square3 :: Int -> Int
-- ^You can put the comment underneath if you like, like this
square3 x = x * x
{-|
Haskell block comments
are also supported
-}
square4 :: Int -> Int
square4 x = x * x
-- |This is a documentation comment for the following datatype
data Tree a = Leaf a | Node [Tree a]
-- |This is a documentation comment for the following type class
class Foo a where
bar :: a |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Icon_and_Unicon | Icon and Unicon | ############################################################################
#
# File: filename.icn
#
# Subject: Short Description
#
# Author: Author's name
#
# Date: Date
#
############################################################################
#
# This file is in the public domain. (or other license)
#
############################################################################
#
# Long form docmentation
#
############################################################################
#
# Links:
#
############################################################################
procedure x1() #: short description of procedure
|
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #Haskell | Haskell | mean :: (Fractional a, Foldable t) => t a -> a
mean lst = sum lst / fromIntegral (length lst)
meanSq :: Fractional c => c -> [c] -> c
meanSq x = mean . map (\y -> (x-y)^^2)
diversityPrediction x estimates = do
putStrLn $ "TrueValue:\t" ++ show x
putStrLn $ "CrowdEstimates:\t" ++ show estimates
let avg = mean estimates
let avgerr = meanSq x estimates
putStrLn $ "AverageError:\t" ++ show avgerr
let crowderr = (x - avg)^^2
putStrLn $ "CrowdError:\t" ++ show crowderr
let diversity = meanSq avg estimates
putStrLn $ "Diversity:\t" ++ show diversity |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #J | J |
echo 'Use: ' , (;:inv 2 {. ARGV) , ' <reference value> <observations>'
data=: ([: ". [: ;:inv 2&}.) ::([: exit 1:) ARGV
([: exit (1: echo@('insufficient data'"_)))^:(2 > #) data
mean=: +/ % #
variance=: [: mean [: *: -
averageError=: ({. variance }.)@:]
crowdError=: variance {.
diversity=: variance }.
echo (<;._2'average error;crowd error;diversity;') ,: ;/ (averageError`crowdError`diversity`:0~ mean@:}.) data
exit 0
|
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #SVG | SVG |
class Sphere: UIView{
override func drawRect(rect: CGRect)
{
let context = UIGraphicsGetCurrentContext()
let locations: [CGFloat] = [0.0, 1.0]
let colors = [UIColor.whiteColor().CGColor,
UIColor.blueColor().CGColor]
let colorspace = CGColorSpaceCreateDeviceRGB()
let gradient = CGGradientCreateWithColors(colorspace,
colors, locations)
var startPoint = CGPoint()
var endPoint = CGPoint()
startPoint.x = self.center.x - (self.frame.width * 0.1)
startPoint.y = self.center.y - (self.frame.width * 0.15)
endPoint.x = self.center.x
endPoint.y = self.center.y
let startRadius: CGFloat = 0
let endRadius: CGFloat = self.frame.width * 0.38
CGContextDrawRadialGradient (context, gradient, startPoint,
startRadius, endPoint, endRadius,
0)
}
}
var s = Sphere(frame: CGRectMake(0, 0, 200, 200))
|
http://rosettacode.org/wiki/Doubly-linked_list/Definition | Doubly-linked list/Definition | Define the data structure for a complete Doubly Linked List.
The structure should support adding elements to the head, tail and middle of the list.
The structure should not allow circular loops
See also
Array
Associative array: Creation, Iteration
Collections
Compound data type
Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
Linked list
Queue: Definition, Usage
Set
Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
Stack
| #Ada | Ada | # -*- coding: utf-8 -*- #
COMMENT REQUIRES:
MODE VALUE = ~;
# For example: #
MODE VALUE = UNION(INT, REAL, COMPL)
END COMMENT
MODE LINKNEW = STRUCT (
LINK next, prev,
VALUE value
);
MODE LINK = REF LINKNEW;
SKIP |
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #Julia | Julia | using DataFrames
text = """
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
"""
const bcolor = ["background: #ffffaa;", "background: #ffdddd;",
"background: #ddffdd;", "background: #ddddff;"]
colorstring(n) = bcolor[n == 1 ? 1 : mod1(n - 1, length(bcolor) - 1) + 1]
function processtable(txt)
df = DataFrame()
indents = Int[]
linetext = String[]
for line in split(txt, "\n")
if length(line) > 0
n = findfirst(!isspace, line)
push!(linetext, String(line[n:end]))
push!(indents, n - 1)
end
end
len = length(indents)
divisor = gcd(indents)
indents .= div.(indents, divisor)
parent(i) = (n = findlast(x -> indents[x] < indents[i], 1:i-1)) == nothing ? 0 : n
children(i) = findall(x -> parent(x) == i, 1:len)
treesize(i) = (s = children(i); isempty(s) ? 1 : sum(treesize, s))
prioronlevel(i) = (j = indents[i]; filter(x -> indents[x] == j, 1:i-1))
treesizeprior(i) = (s = prioronlevel(i); isempty(s) ? 0 : sum(treesize, s))
startpos(i) = (n = parent(i)) == 0 ? 0 : treesizeprior(n) - treesizeprior(i)
function leveloneparent(i)
p = parent(i)
return p < 1 ? 1 : p ==1 ? sum(x -> indents[x] <= 1, 1:i) : leveloneparent(p)
end
df.TEXT = linetext
df.INDENT = indents
df.COLSPAN = [treesize(i) for i in 1:len]
df.PRESPAN = [max(0, startpos(i)) for i in 1:len]
df.LEVELONEPARENT = [leveloneparent(i) for i in 1:len]
return df
end
function htmlfromdataframe(df)
println("<h4>A Rosetta Code Nested Table</h4><table style=\"width:100%\" class=\"wikitable\" >")
for ind in minimum(df.INDENT):maximum(df.INDENT)
println("<tr>")
for row in eachrow(df)
if row[:INDENT] == ind
if row[:PRESPAN] > 0
println("<td colspan=\"$(row[:PRESPAN])\"> </td>")
end
print("<td ")
if row[:COLSPAN] > 0
println("colspan=\"$(row[:COLSPAN])\"")
end
println(" style = \"$(colorstring(row[:LEVELONEPARENT]))\" >$(row[:TEXT])</td>")
end
end
println("</tr>")
end
println("</table>")
end
htmlfromdataframe(processtable(text))
textplus = text * " Optionally add color to the nodes."
htmlfromdataframe(processtable(textplus))
|
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #Mathematica_.2F_Wolfram_Language | Mathematica / Wolfram Language | s = "Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.";
s = StringSplit[s, "\n"];
indentation = LengthWhile[Characters[#], EqualTo[" "]] & /@ s;
s = MapThread[StringDrop, {s, indentation}];
indentation =
indentation /.
Thread[Union[indentation] -> Range[Length[Union[indentation]]]];
ii = Transpose[{Range[Length[indentation]], indentation}];
(*ii//Grid*)
sel = Table[
{i, Last@Select[ii, #[[2]] < i[[2]] \[And] #[[1]] < i[[1]] &]}
,
{i, Rest@ii}
];
g = Graph[Rule @@@ sel[[All, All, 1]], VertexLabels -> "Name"];
vl = VertexList[g];
head = FirstPosition[vl, 1][[1]];
dm = GraphDistanceMatrix[g];
depth = ReverseSortBy[Transpose[{vl, dm[[All, head]]}], Last];
colspandb = <||>;
data = Table[
vert = d[[1]];
vd = VertexInDegree[g, vert];
vics = VertexInComponent[g, vert, {1}];
vocs = Rest@VertexOutComponent[g, vert];
cspan = 0;
Do[
If[KeyExistsQ[colspandb, vic],
cspan += colspandb[vic]
]
,
{vic, vics}
];
If[cspan == 0, cspan = 1];
AssociateTo[colspandb, d[[1]] -> cspan];
{Sequence @@ d, vd, vics, vocs, cspan}
,
{d, depth}
];
emptybefore = Table[
{d[[1]],
Length@
Select[
data, #[[1]] < d[[1]] \[And]
Length[#[[4]]] == 0 \[And] #[[2]] < d[[2]] &][[All, {1, 2,
3}]]}
,
{d, data}
];
emptybefore = Association[Rule @@@ emptybefore];
depthcopy = depth;
depthcopy[[All, 2]] += 1;
graphelements =
SortBy[Sort /@ GatherBy[depthcopy, Last], First /* Last][[All, All,
1]];
str = {"<table style='text-align: center;'>"};
colorsdb = <|1 -> "#ffffe6", 2 -> "#ffebd2", 6 -> "#f0fff0",
10 -> "#e6ffff"|>;
Do[
AppendTo[str, "<tr>"];
totalspan = 0;
Do[
If[KeyExistsQ[colorsdb, g],
color = colorsdb[g]
,
(*Print["sel",SelectFirst[data,First/*EqualTo[g]][[5]]];*)
color =
colorsdb[
Max[
Intersection[SelectFirst[data, First /* EqualTo[g]][[5]],
Keys[colorsdb]]]]
];
span = SelectFirst[data, First /* EqualTo[g]][[6]];
totalspan += span;
empty = emptybefore[g];
str = str~Join~
ConstantArray["<td style=\"background-color: #F9F9F9;\"></td>",
empty];
If[span == 1,
AppendTo[str,
"<td style=\"background-color: " <> color <> ";\">" <> s[[g]] <>
"</td>"];
,
AppendTo[str,
"<tdcolspan=\"" <> ToString[span] <>
"\" style=\"background-color: " <> color <> ";\">" <> s[[g]] <>
"</td>"];
];
,
{g, ge}
];
extra =
SelectFirst[data, First /* EqualTo[1]][[6]] - totalspan - empty;
str = str~Join~
ConstantArray["<td style=\"background-color: #F9F9F9;\"></td>",
extra];
AppendTo[str, "</tr>"];
,
{ge, graphelements}
]
AppendTo[str, "</table>"];
StringRiffle[str, "\n"] |
http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #Sidef | Sidef | STDOUT.autoflush(true)
var (rows, cols) = `stty size`.nums...
var x = (rows/2 - 1 -> int)
var y = (cols/2 - 16 -> int)
var chars = [
"┌─┐ ╷╶─┐╶─┐╷ ╷┌─╴┌─╴╶─┐┌─┐┌─┐ ",
"│ │ │┌─┘╶─┤└─┤└─┐├─┐ │├─┤└─┤ : ",
"└─┘ ╵└─╴╶─┘ ╵╶─┘└─┘ ╵└─┘╶─┘ "
].map {|s| s.split(3) }
func position(i,j) {
"\e[%d;%dH" % (i, j)
}
func indices {
var t = Time.local
"%02d:%02d:%02d" % (t.hour, t.min, t.sec) -> split(1).map{|c| c.ord - '0'.ord }
}
loop {
print "\e[H\e[J"
for i in ^chars {
print position(x + i, y)
print [chars[i][indices()]].join(' ')
}
print position(1, 1)
Sys.sleep(0.1)
} |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Julia | Julia | # From Julia 1.0's online docs. File countheads.jl available to all machines:
function count_heads(n)
c::Int = 0
for i = 1:n
c += rand(Bool)
end
c
end |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #LFE | LFE |
$ ./bin/lfe
Erlang/OTP 17 [erts-6.2] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]
LFE Shell V6.2 (abort with ^G)
>
|
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Factor | Factor | USING: dns io kernel sequences ;
"www.kame.net" [ dns-A-query ] [ dns-AAAA-query ] bi
[ message>names second print ] bi@ |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Frink | Frink | for a = callJava["java.net.InetAddress", "getAllByName", "www.kame.net"]
println[a.getHostAddress[]] |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Go | Go | package main
import (
"fmt"
"net"
)
func main() {
if addrs, err := net.LookupHost("www.kame.net"); err == nil {
fmt.Println(addrs)
} else {
fmt.Println(err)
}
} |
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #Perl | Perl | use SVG;
use List::Util qw(max min);
use constant pi => 2 * atan2(1, 0);
# Compute the curve with a Lindemayer-system
my %rules = (
X => 'X+YF+',
Y => '-FX-Y'
);
my $dragon = 'FX';
$dragon =~ s/([XY])/$rules{$1}/eg for 1..10;
# Draw the curve in SVG
($x, $y) = (0, 0);
$theta = 0;
$r = 6;
for (split //, $dragon) {
if (/F/) {
push @X, sprintf "%.0f", $x;
push @Y, sprintf "%.0f", $y;
$x += $r * cos($theta);
$y += $r * sin($theta);
}
elsif (/\+/) { $theta += pi/2; }
elsif (/\-/) { $theta -= pi/2; }
}
$xrng = max(@X) - min(@X);
$yrng = max(@Y) - min(@Y);
$xt = -min(@X)+10;
$yt = -min(@Y)+10;
$svg = SVG->new(width=>$xrng+20, height=>$yrng+20);
$points = $svg->get_path(x=>\@X, y=>\@Y, -type=>'polyline');
$svg->rect(width=>"100%", height=>"100%", style=>{'fill'=>'black'});
$svg->polyline(%$points, style=>{'stroke'=>'orange', 'stroke-width'=>1}, transform=>"translate($xt,$yt)");
open $fh, '>', 'dragon_curve.svg';
print $fh $svg->xmlify(-namespace=>'svg');
close $fh; |
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #Groovy | Groovy | class LinearCombination {
private static String linearCombo(int[] c) {
StringBuilder sb = new StringBuilder()
for (int i = 0; i < c.length; ++i) {
if (c[i] == 0) continue
String op
if (c[i] < 0 && sb.length() == 0) {
op = "-"
} else if (c[i] < 0) {
op = " - "
} else if (c[i] > 0 && sb.length() == 0) {
op = ""
} else {
op = " + "
}
int av = Math.abs(c[i])
String coeff = av == 1 ? "" : "" + av + "*"
sb.append(op).append(coeff).append("e(").append(i + 1).append(')')
}
if (sb.length() == 0) {
return "0"
}
return sb.toString()
}
static void main(String[] args) {
int[][] combos = [
[1, 2, 3],
[0, 1, 2, 3],
[1, 0, 3, 4],
[1, 2, 0],
[0, 0, 0],
[0],
[1, 1, 1],
[-1, -1, -1],
[-1, -2, 0, -3],
[-1]
]
for (int[] c : combos) {
printf("%-15s -> %s\n", Arrays.toString(c), linearCombo(c))
}
}
} |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Isabelle | Isabelle | theory Text
imports Main
begin
chapter ‹Presenting Theories›
text ‹This text will appear in the proof document.›
section ‹Some Examples.›
― ‹A marginal comment. The expression \<^term>‹True› holds.›
lemma True_is_True: "True" ..
text ‹
The overall content of an Isabelle/Isar theory may alternate between formal
and informal text.
›
text_raw ‹Can also contain raw latex.›
text ‹This text will only compile if the fact @{thm True_is_True} holds.›
text ‹This text will only compile if the constant \<^const>‹True› is defined.›
end |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #J | J | NB. =========================================================
NB.*apply v apply verb x to y
apply=: 128!:2
NB. =========================================================
NB.*def c : (explicit definition)
def=: :
NB.*define a : 0 (explicit definition script form)
define=: : 0
NB.*do v name for ".
do=: ".
NB.*drop v name for }.
drop=: }.
Note 1
Note accepts multi-line descriptions.
Definitions display the source.
)
usleep
3 : '''libc.so.6 usleep > i i''&(15!:0) >.y'
|
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Java | Java | /**
* This is a class documentation comment. This text shows at the top of the page for this class
* @author Joe Schmoe
*/
public class Doc{
/**
* This is a field comment for a variable
*/
private String field;
/**
* This is a method comment. It has parameter tags (param), an exception tag (throws),
* and a return value tag (return).
*
* @param num a number with the variable name "num"
* @throws BadException when something bad happens
* @return another number
*/
public int method(long num) throws BadException{
//...code here
}
} |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #Java | Java | import java.util.Arrays;
public class DiversityPredictionTheorem {
private static double square(double d) {
return d * d;
}
private static double averageSquareDiff(double d, double[] predictions) {
return Arrays.stream(predictions)
.map(it -> square(it - d))
.average()
.orElseThrow();
}
private static String diversityTheorem(double truth, double[] predictions) {
double average = Arrays.stream(predictions)
.average()
.orElseThrow();
return String.format("average-error : %6.3f%n", averageSquareDiff(truth, predictions))
+ String.format("crowd-error : %6.3f%n", square(truth - average))
+ String.format("diversity : %6.3f%n", averageSquareDiff(average, predictions));
}
public static void main(String[] args) {
System.out.println(diversityTheorem(49.0, new double[]{48.0, 47.0, 51.0}));
System.out.println(diversityTheorem(49.0, new double[]{48.0, 47.0, 51.0, 42.0}));
}
} |
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #Swift | Swift |
class Sphere: UIView{
override func drawRect(rect: CGRect)
{
let context = UIGraphicsGetCurrentContext()
let locations: [CGFloat] = [0.0, 1.0]
let colors = [UIColor.whiteColor().CGColor,
UIColor.blueColor().CGColor]
let colorspace = CGColorSpaceCreateDeviceRGB()
let gradient = CGGradientCreateWithColors(colorspace,
colors, locations)
var startPoint = CGPoint()
var endPoint = CGPoint()
startPoint.x = self.center.x - (self.frame.width * 0.1)
startPoint.y = self.center.y - (self.frame.width * 0.15)
endPoint.x = self.center.x
endPoint.y = self.center.y
let startRadius: CGFloat = 0
let endRadius: CGFloat = self.frame.width * 0.38
CGContextDrawRadialGradient (context, gradient, startPoint,
startRadius, endPoint, endRadius,
0)
}
}
var s = Sphere(frame: CGRectMake(0, 0, 200, 200))
|
http://rosettacode.org/wiki/Doubly-linked_list/Definition | Doubly-linked list/Definition | Define the data structure for a complete Doubly Linked List.
The structure should support adding elements to the head, tail and middle of the list.
The structure should not allow circular loops
See also
Array
Associative array: Creation, Iteration
Collections
Compound data type
Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
Linked list
Queue: Definition, Usage
Set
Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
Stack
| #ALGOL_68 | ALGOL 68 | # -*- coding: utf-8 -*- #
COMMENT REQUIRES:
MODE VALUE = ~;
# For example: #
MODE VALUE = UNION(INT, REAL, COMPL)
END COMMENT
MODE LINKNEW = STRUCT (
LINK next, prev,
VALUE value
);
MODE LINK = REF LINKNEW;
SKIP |
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #Nim | Nim | import strutils
const Outline = """Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML."""
type Color {.pure.} = enum
NoColor
Yellow = "#ffffe6;"
Orange = "#ffebd2;"
Green = "#f0fff0;"
Blue = "#e6ffff;"
const Line1Color = Yellow
const Line2Colors = [Orange, Green, Blue]
type Node = ref object
value: string
level: Natural
width: Natural
color: Color
parent: Node
children: seq[Node]
#---------------------------------------------------------------------------------------------------
proc leadingSpaces(line: string): int =
## return the number of leading spaces.
while line[result] == ' ':
inc result
#---------------------------------------------------------------------------------------------------
proc buildTree(outline: string): tuple[root: Node, depth: Natural] =
## Build the tree for the given outline.
result.root = Node()
var level: int
var startPos = @[-1]
var nodes: seq[Node] = @[result.root]
var linecount = 0
for line in Outline.splitLines:
inc linecount
if line.len == 0: continue
let start = line.leadingSpaces()
level = startPos.find(start)
if level < 0:
# Level not yet encountered.
if start < startPos[^1]:
raise newException(ValueError, "wrong indentation at line " & $linecount)
startPos.add(start)
nodes.add(nil)
level = startPos.high
# Create the node.
let node = Node(value: line.strip(), level: level)
let parent = nodes[level - 1]
parent.children.add(node)
node.parent = parent
nodes[level] = node # Set the node as current node for this level.
result.depth = nodes.high
#---------------------------------------------------------------------------------------------------
proc padTree(node: Node; depth: Natural) =
## pad the tree with empty nodes to get an even depth.
if node.level == depth:
return
if node.children.len == 0:
# Add an empty node.
node.children.add(Node(level: node.level + 1, parent: node))
for child in node.children:
child.padTree(depth)
#---------------------------------------------------------------------------------------------------
proc computeWidths(node: Node) =
## Compute the widths.
var width = 0
if node.children.len == 0:
width = 1
else:
for child in node.children:
child.computeWidths()
inc width, child.width
node.width = width
#---------------------------------------------------------------------------------------------------
proc build(nodelists: var seq[seq[Node]]; node: Node) =
## Build the list of nodes per level.
nodelists[node.level].add(node)
for child in node.children:
nodelists.build(child)
#---------------------------------------------------------------------------------------------------
proc setColors(nodelists: seq[seq[Node]]) =
## Set the colors of the nodes.
for node in nodelists[1]:
node.color = Line1Color
for i, node in nodelists[2]:
node.color = Line2Colors[i mod Line2Colors.len]
for level in 3..nodelists.high:
for node in nodelists[level]:
node.color = if node.value.len != 0: node.parent.color else: NoColor
#---------------------------------------------------------------------------------------------------
proc writeWikiTable(nodelists: seq[seq[Node]]) =
## Output the wikitable.
echo "{| class='wikitable' style='text-align: center;'"
for level in 1..nodelists.high:
echo "|-"
for node in nodelists[level]:
if node.width > 1:
# Node with children.
echo "| style='background: $1 ' colspan=$2 | $3".format(node.color, node.width, node.value)
elif node.value.len > 0:
# Leaf with contents.
echo "| style='background: $1 ' | $2".format(node.color, node.value)
else:
# Empty cell.
echo "| | "
echo "|}"
#---------------------------------------------------------------------------------------------------
proc writeHtml(nodelists: seq[seq[Node]]) =
## Output the HTML.
echo "<table class='wikitable' style='text-align: center;'>"
for level in 1..nodelists.high:
echo " <tr>"
for node in nodelists[level]:
if node.width > 1:
# Node with children.
echo " <td colspan='$1' style='background-color: $2'>$3</td>".format(node.width, node.color, node.value)
elif node.value.len > 0:
# Leaf with contents.
echo " <td style='background-color: $1'>$2</td>".format(node.color, node.value)
else:
# Empty cell.
echo " <td></td>"
echo " </tr>"
echo "</table>"
#———————————————————————————————————————————————————————————————————————————————————————————————————
let (root, depth) = Outline.buildTree()
root.padTree(depth)
root.computeWidths()
var nodelists = newSeq[seq[Node]](depth + 1)
nodelists.build(root)
nodelists.setColors()
echo "WikiTable:"
nodelists.writeWikiTable()
echo "HTML:"
nodelists.writeHtml() |
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #Perl | Perl | #!/usr/bin/perl
use strict;
use warnings;
my @rows;
my $row = -1;
my $width = 0;
my $color = 0;
our $bg = 'e0ffe0';
parseoutline( do { local $/; <DATA> =~ s/\t/ /gr } );
print "<table border=1 cellspacing=0>\n";
for ( @rows )
{
my $start = 0;
print " <tr>\n";
for ( @$_ ) # columns
{
my ($data, $col, $span, $bg) = @$_;
print " <td></td>\n" x ( $col - $start ),
" <td colspan=$span align=center bgcolor=#$bg> $data </td>\n";
$start = $col + $span;
}
print " <td></td>\n" x ( $width - $start ), " </tr>\n";
}
print "</table>\n";
sub parseoutline
{
++$row;
while( $_[0] =~ /^( *)(.*)\n((?:\1 .*\n)*)/gm )
{
my ($head, $body, $col) = ($2, $3, $width);
$row == 1 and local $bg = qw( ffffe0 ffe0e0 )[ $color ^= 1];
if( length $body ) { parseoutline( $body ) } else { ++$width }
push @{ $rows[$row] }, [ $head, $col, $width - $col, $bg ];
}
--$row;
}
__DATA__
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML. |
http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #SVG | SVG | <svg viewBox="0 0 100 100" width="480px" height="480px" xmlns="http://www.w3.org/2000/svg">
<circle cx="50" cy="50" r="48" style="fill:peru; stroke:black; stroke-width:2" />
<g transform="translate(50,50) rotate(0)" style="fill:none; stroke-linecap:round">
<line y2="-36" style="stroke:black; stroke-width:5">
<animateTransform
attributeName="transform"
type="rotate"
by="30"
dur="3600s"
accumulate="sum"
repeatCount="indefinite"/>
</line>
<line y2="-42" style="stroke:white; stroke-width:2">
<animateTransform
attributeName="transform"
type="rotate"
by="6"
dur="60s"
accumulate="sum"
repeatCount="indefinite"/>
</line>
<line y2="-46" style="stroke:red; stroke-width:1">
<animateTransform
attributeName="transform"
type="rotate"
calcMode="discrete"
by="6"
dur="1s"
accumulate="sum"
repeatCount="indefinite"/>
</line>
</g>
<circle cx="50" cy="50" r="4" style="fill:gold; stroke:black; stroke-width:1" />
</svg>
|
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Mathematica_.2F_Wolfram_Language | Mathematica / Wolfram Language | LaunchKernels[2];
ParallelEvaluate[RandomReal[]]
|
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Nim | Nim | import os, nanomsg
proc sendMsg(s: cint, msg: string) =
echo "SENDING \"",msg,"\""
let bytes = s.send(msg.cstring, msg.len + 1, 0)
assert bytes == msg.len + 1
proc recvMsg(s: cint) =
var buf: cstring
let bytes = s.recv(addr buf, MSG, 0)
if bytes > 0:
echo "RECEIVED \"",buf,"\""
discard freemsg buf
proc sendRecv(s: cint, msg: string) =
var to: cint = 100
discard s.setSockOpt(SOL_SOCKET, RCVTIMEO, addr to, sizeof to)
while true:
s.recvMsg
sleep 1000
s.sendMsg msg
proc node0(url: string) =
var s = socket(AF_SP, nanomsg.PAIR)
assert s >= 0
let res = s.bindd url
assert res >= 0
s.sendRecv "node0"
discard s.shutdown 0
proc node1(url: string) =
var s = socket(AF_SP, nanomsg.PAIR)
assert s >= 0
let res = s.connect url
assert res >= 0
s.sendRecv "node1"
discard s.shutdown 0
if paramStr(1) == "node0":
node0 paramStr(2)
elif paramStr(1) == "node1":
node1 paramStr(2) |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Groovy | Groovy | def addresses = InetAddress.getAllByName('www.kame.net')
println "IPv4: ${addresses.find { it instanceof Inet4Address }?.hostAddress}"
println "IPv6: ${addresses.find { it instanceof Inet6Address }?.hostAddress}" |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Haskell | Haskell | module Main where
import Network.Socket
getWebAddresses :: HostName -> IO [SockAddr]
getWebAddresses host = do
results <- getAddrInfo (Just defaultHints) (Just host) (Just "http")
return [ addrAddress a | a <- results, addrSocketType a == Stream ]
showIPs :: HostName -> IO ()
showIPs host = do
putStrLn $ "IP addresses for " ++ host ++ ":"
addresses <- getWebAddresses host
mapM_ (putStrLn . (" "++) . show) addresses
main = showIPs "www.kame.net"
|
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #Phix | Phix | --
-- demo\rosetta\DragonCurve.exw
-- ============================
--
with javascript_semantics
include pGUI.e
Ihandle dlg, canvas
cdCanvas cddbuffer, cdcanvas
integer colour = 0
procedure Dragon(integer depth, atom x1, y1, x2, y2)
depth -= 1
if depth<=0 then
cdCanvasSetForeground(cddbuffer, colour)
cdCanvasLine(cddbuffer, x1, y1, x2, y2)
-- (some interesting colour patterns emerge)
colour += 2
-- colour += 2000
-- colour += #100
else
atom dx = x2-x1, dy = y2-y1,
nx = x1+(dx-dy)/2,
ny = y1+(dx+dy)/2
Dragon(depth,x1,y1,nx,ny)
Dragon(depth,x2,y2,nx,ny)
end if
end procedure
function redraw_cb(Ihandle /*ih*/, integer /*posx*/, /*posy*/)
cdCanvasActivate(cddbuffer)
cdCanvasClear(cddbuffer)
-- (note: depths over 21 take a long time to draw,
-- depths <= 16 look a little washed out)
Dragon(17,100,100,100+256,100)
cdCanvasFlush(cddbuffer)
return IUP_DEFAULT
end function
function map_cb(Ihandle ih)
cdcanvas = cdCreateCanvas(CD_IUP, ih)
cddbuffer = cdCreateCanvas(CD_DBUFFER, cdcanvas)
cdCanvasSetBackground(cddbuffer, CD_PARCHMENT)
return IUP_DEFAULT
end function
procedure main()
IupOpen()
canvas = IupCanvas(NULL)
IupSetAttribute(canvas, "RASTERSIZE", "420x290")
IupSetCallback(canvas, "MAP_CB", Icallback("map_cb"))
IupSetCallback(canvas, "ACTION", Icallback("redraw_cb"))
dlg = IupDialog(canvas,"RESIZE=NO")
IupSetAttribute(dlg, "TITLE", "Dragon Curve")
IupShow(dlg)
if platform()!=JS then
IupMainLoop()
IupClose()
end if
end procedure
main()
|
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #Haskell | Haskell | import Text.Printf (printf)
linearForm :: [Int] -> String
linearForm = strip . concat . zipWith term [1..]
where
term :: Int -> Int -> String
term i c = case c of
0 -> mempty
1 -> printf "+e(%d)" i
-1 -> printf "-e(%d)" i
c -> printf "%+d*e(%d)" c i
strip str = case str of
'+':s -> s
"" -> "0"
s -> s |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Julia | Julia |
"Tell whether there are too foo items in the array."
foo(xs::Array) = ...
|
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Kotlin | Kotlin | /**
* A group of *members*.
* @author A Programmer.
* @since version 1.1.51.
*
* This class has no useful logic; it's just a documentation example.
*
* @param T the type of a member in this group.
* @property name the name of this group.
* @constructor Creates an empty group.
*/
class Group<T>(val name: String) {
/**
* Adds a [member] to this group.
* @throws AddException if the member can't be added.
* @return the new size of the group.
*/
fun add(member: T): Int { ... }
} |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Lambdatalk | Lambdatalk |
'{def add // define the name
{lambda {:a :b} // for a function with two arguments
{+ :a :b} // whose body calls the + primitive on them
} // end function
} // end define
-> add
'{add 3 4} // call the function on two values
-> 7 // the result
|
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #JavaScript | JavaScript | 'use strict';
function sum(array) {
return array.reduce(function (a, b) {
return a + b;
});
}
function square(x) {
return x * x;
}
function mean(array) {
return sum(array) / array.length;
}
function averageSquareDiff(a, predictions) {
return mean(predictions.map(function (x) {
return square(x - a);
}));
}
function diversityTheorem(truth, predictions) {
var average = mean(predictions);
return {
'average-error': averageSquareDiff(truth, predictions),
'crowd-error': square(truth - average),
'diversity': averageSquareDiff(average, predictions)
};
}
console.log(diversityTheorem(49, [48,47,51]))
console.log(diversityTheorem(49, [48,47,51,42]))
|
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #Tcl | Tcl | proc grey {n} {format "#%2.2x%2.2x%2.2x" $n $n $n}
pack [canvas .c -height 400 -width 640 -background white]
for {set i 0} {$i < 255} {incr i} {
set h [grey $i]
.c create arc [expr {100+$i/5}] [expr {50+$i/5}] [expr {400-$i/1.5}] [expr {350-$i/1.5}] \
-start 0 -extent 359 -fill $h -outline $h
} |
http://rosettacode.org/wiki/Doubly-linked_list/Definition | Doubly-linked list/Definition | Define the data structure for a complete Doubly Linked List.
The structure should support adding elements to the head, tail and middle of the list.
The structure should not allow circular loops
See also
Array
Associative array: Creation, Iteration
Collections
Compound data type
Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
Linked list
Queue: Definition, Usage
Set
Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
Stack
| #ARM_Assembly | ARM Assembly |
/* ARM assembly Raspberry PI */
/* program defDblList.s */
/* Constantes */
.equ STDOUT, 1 @ Linux output console
.equ EXIT, 1 @ Linux syscall
.equ READ, 3
.equ WRITE, 4
/*******************************************/
/* Structures */
/********************************************/
/* structure Doublylinkedlist*/
.struct 0
dllist_head: @ head node
.struct dllist_head + 4
dllist_tail: @ tail node
.struct dllist_tail + 4
dllist_fin:
/* structure Node Doublylinked List*/
.struct 0
NDlist_next: @ next element
.struct NDlist_next + 4
NDlist_prev: @ previous element
.struct NDlist_prev + 4
NDlist_value: @ element value or key
.struct NDlist_value + 4
NDlist_fin:
/* Initialized data */
.data
szMessInitListe: .asciz "List initialized.\n"
szCarriageReturn: .asciz "\n"
szMessErreur: .asciz "Error detected.\n"
/* UnInitialized data */
.bss
dllist1: .skip dllist_fin @ list memory place
/* code section */
.text
.global main
main:
ldr r0,iAdrdllist1
bl newDList @ create new list
ldr r0,iAdrszMessInitListe
bl affichageMess
ldr r0,iAdrdllist1 @ list address
mov r1,#10 @ value
bl insertHead @ insertion at head
cmp r0,#-1
beq 99f
ldr r0,iAdrdllist1
mov r1,#20
bl insertTail @ insertion at tail
cmp r0,#-1
beq 99f
ldr r0,iAdrdllist1 @ list address
mov r1,#10 @ value to after insered
mov r2,#15 @ new value
bl insertAfter
cmp r0,#-1
beq 99f
b 100f
99:
ldr r0,iAdrszMessErreur
bl affichageMess
100: @ standard end of the program
mov r7, #EXIT @ request to exit program
svc 0 @ perform system call
iAdrszMessInitListe: .int szMessInitListe
iAdrszMessErreur: .int szMessErreur
iAdrszCarriageReturn: .int szCarriageReturn
iAdrdllist1: .int dllist1
/******************************************************************/
/* create new list */
/******************************************************************/
/* r0 contains the address of the list structure */
newDList:
push {r1,lr} @ save registers
mov r1,#0
str r1,[r0,#dllist_tail]
str r1,[r0,#dllist_head]
pop {r1,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* list is empty ? */
/******************************************************************/
/* r0 contains the address of the list structure */
/* r0 return 0 if empty else return 1 */
isEmpty:
//push {r1,lr} @ save registers
ldr r0,[r0,#dllist_head]
cmp r0,#0
movne r0,#1
//pop {r1,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* insert value at list head */
/******************************************************************/
/* r0 contains the address of the list structure */
/* r1 contains value */
insertHead:
push {r1-r4,lr} @ save registers
mov r4,r0 @ save address
mov r0,r1 @ value
bl createNode
cmp r0,#-1 @ allocation error ?
beq 100f
ldr r2,[r4,#dllist_head] @ load address first node
str r2,[r0,#NDlist_next] @ store in next pointer on new node
mov r1,#0
str r1,[r0,#NDlist_prev] @ store zero in previous pointer on new node
str r0,[r4,#dllist_head] @ store address new node in address head list
cmp r2,#0 @ address first node is null ?
strne r0,[r2,#NDlist_prev] @ no store adresse new node in previous pointer
streq r0,[r4,#dllist_tail] @ else store new node in tail address
100:
pop {r1-r4,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* insert value at list tail */
/******************************************************************/
/* r0 contains the address of the list structure */
/* r1 contains value */
insertTail:
push {r1-r4,lr} @ save registers
mov r4,r0 @ save list address
mov r0,r1 @ value
bl createNode @ create new node
cmp r0,#-1
beq 100f @ allocation error
ldr r2,[r4,#dllist_tail] @ load address last node
str r2,[r0,#NDlist_prev] @ store in previous pointer on new node
mov r1,#0 @ store null un next pointer
str r1,[r0,#NDlist_next]
str r0,[r4,#dllist_tail] @ store address new node on list tail
cmp r2,#0 @ address last node is null ?
strne r0,[r2,#NDlist_next] @ no store address new node in next pointer
streq r0,[r4,#dllist_head] @ else store in head list
100:
pop {r1-r4,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* insert value after other element */
/******************************************************************/
/* r0 contains the address of the list structure */
/* r1 contains value to search*/
/* r2 contains value to insert */
insertAfter:
push {r1-r5,lr} @ save registers
mov r4,r0 @ save list address
bl searchValue @ search this value in r1
cmp r0,#-1
beq 100f @ not found -> error
mov r5,r0 @ save address of node find
mov r0,r2 @ new value
bl createNode @ create new node
cmp r0,#-1
beq 100f @ allocation error
ldr r2,[r5,#NDlist_next] @ load pointer next of find node
str r0,[r5,#NDlist_next] @ store new node in pointer next
str r5,[r0,#NDlist_prev] @ store address find node in previous pointer on new node
str r2,[r0,#NDlist_next] @ store pointer next of find node on pointer next on new node
cmp r2,#0 @ next pointer is null ?
strne r0,[r2,#NDlist_prev] @ no store address new node in previous pointer
streq r0,[r4,#dllist_tail] @ else store in list tail
100:
pop {r1-r5,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* search value */
/******************************************************************/
/* r0 contains the address of the list structure */
/* r1 contains the value to search */
/* r0 return address of node or -1 if not found */
searchValue:
push {r2,lr} @ save registers
ldr r0,[r0,#dllist_head] @ load first node
1:
cmp r0,#0 @ null -> end search not found
moveq r0,#-1
beq 100f
ldr r2,[r0,#NDlist_value] @ load node value
cmp r2,r1 @ equal ?
beq 100f
ldr r0,[r0,#NDlist_next] @ load addresse next node
b 1b @ and loop
100:
pop {r2,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* Create new node */
/******************************************************************/
/* r0 contains the value */
/* r0 return node address or -1 if allocation error*/
createNode:
push {r1-r7,lr} @ save registers
mov r4,r0 @ save value
@ allocation place on the heap
mov r0,#0 @ allocation place heap
mov r7,#0x2D @ call system 'brk'
svc #0
mov r5,r0 @ save address heap for output string
add r0,#NDlist_fin @ reservation place one element
mov r7,#0x2D @ call system 'brk'
svc #0
cmp r0,#-1 @ allocation error
beq 100f
mov r0,r5
str r4,[r0,#NDlist_value] @ store value
mov r2,#0
str r2,[r0,#NDlist_next] @ store zero to pointer next
str r2,[r0,#NDlist_prev] @ store zero to pointer previous
100:
pop {r1-r7,lr} @ restaur registers
bx lr @ return
/******************************************************************/
/* display text with size calculation */
/******************************************************************/
/* r0 contains the address of the message */
affichageMess:
push {r0,r1,r2,r7,lr} @ save registers
mov r2,#0 @ counter length */
1: @ loop length calculation
ldrb r1,[r0,r2] @ read octet start position + index
cmp r1,#0 @ if 0 its over
addne r2,r2,#1 @ else add 1 in the length
bne 1b @ and loop
@ so here r2 contains the length of the message
mov r1,r0 @ address message in r1
mov r0,#STDOUT @ code to write to the standard output Linux
mov r7, #WRITE @ code call system "write"
svc #0 @ call system
pop {r0,r1,r2,r7,lr} @ restaur registers
bx lr @ return
|
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #Phix | Phix | with javascript_semantics
constant html = false,
outlines = {"""
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.""", """
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
Propagating the sums upward as necessary.
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
Optionally add color to the nodes."""}
constant yellow = "#ffffe6;",
orange = "#ffebd2;",
green = "#f0fff0;",
blue = "#e6ffff;",
pink = "#ffeeff;",
colours = {{yellow, orange, green, blue, pink},
{blue, yellow, orange, green, pink}}
function calc_spans(sequence lines, integer ldx)
sequence children = lines[ldx][$]
if length(children)!=0 then
integer span = 0
for i=1 to length(children) do
integer child = children[i]
lines = calc_spans(lines,child)
span += lines[child][4]
end for
lines[ldx][4] = span
-- else -- (span already 1)
end if
return lines
end function
procedure markup(string outline, sequence colours)
sequence lines = split(outline,"\n",no_empty:=true),
pi = {}, -- indents (to locate parents)
pdx = {}, -- indexes for ""
children = {}
string text
integer maxdepth = 0,
parent, depth, span
for i=1 to length(lines) do
string line = trim_tail(lines[i])
text = trim_head(line)
integer indent = length(line)-length(text)
-- remove any completed parents
while length(pi) and indent<=pi[$] do
pi = pi[1..$-1]
pdx = pdx[1..$-1]
end while
parent = 0
if length(pi) then
parent = pdx[$]
lines[parent][$] = deep_copy(lines[parent][$]) & i -- (update children)
end if
pi &= indent
pdx &= i
depth = length(pi)
span = 1 -- (default/assume no children[=={}])
lines[i] = {i,depth,indent,span,parent,text,children}
maxdepth = max(maxdepth,depth)
end for
lines = calc_spans(lines,1)
string res = iff(html?"<table class=\"wikitable\" style=\"text-align: center;\">\n"
:"{| class=\"wikitable\" style=\"text-align: center;\"\n")
for d=1 to maxdepth do
res &= iff(html?"<tr>\n"
:"|-\n")
integer cdx = 1, lii, lident
for i=1 to length(lines) do
{lii,depth,lident,span,parent,text,children} = lines[i]
if depth=2 then cdx += 1 end if
string style = sprintf(`style="background: %s"`,{colours[cdx]})
if depth=d then
if span!=1 then style &= sprintf(` colspan="%d"`,span) end if
res &= sprintf(iff(html?"<td %s>%s</td>\n"
:"| %s | %s\n"),{style,text})
elsif depth<d and children={} then
-- res &= iff(html?"<td></td>\n"
-- :"| |\n")
res &= sprintf(iff(html?"<td %s></td>\n"
:"| %s |\n"),{style})
end if
end for
if html then
res &= "</tr>\n"
end if
end for
res &= iff(html?"</table>\n"
:"|}\n")
puts(1,res)
end procedure
for i=1 to length(outlines) do
markup(outlines[i],colours[i])
end for
|
http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #Tcl | Tcl | package require Tcl 8.5
package require Tk
# GUI code
pack [canvas .c -width 200 -height 200]
.c create oval 20 20 180 180 -width 10 -fill {} -outline grey70
.c create line 0 0 1 1 -tags hour -width 6 -cap round -fill black
.c create line 0 0 1 1 -tags minute -width 4 -cap round -fill black
.c create line 0 0 1 1 -tags second -width 2 -cap round -fill grey30
proc updateClock t {
scan [clock format $t -format "%H %M %S"] "%d%d%d" h m s
# On an analog clock, the hour and minute hands move gradually
set m [expr {$m + $s/60.0}]
set h [expr {($h % 12 + $m/60.0) * 5}]
foreach tag {hour minute second} value [list $h $m $s] len {50 80 80} {
.c coords $tag 100 100 \
[expr {100 + $len*sin($value/30.0*3.14159)}] \
[expr {100 - $len*cos($value/30.0*3.14159)}]
}
}
# Timer code, accurate to within a quarter second
set time 0
proc ticker {} {
global time
set t [clock seconds]
after 250 ticker
if {$t != $time} {
set time $t
updateClock $t
}
}
ticker |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Objective-C | Objective-C | #import <Foundation/Foundation.h>
// our protocol allows "sending" "strings", but we can implement
// everything we could for a "local" object
@protocol ActionObjectProtocol
- (NSString *)sendMessage: (NSString *)msg;
@end |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #OCaml | OCaml | open Printf
let create_logger () =
def log(text) & logs(l) =
printf "Logged: %s\n%!" text;
logs((text, Unix.gettimeofday ())::l) & reply to log
or search(text) & logs(l) =
logs(l) & reply List.filter (fun (line, _) -> line = text) l to search
in
spawn logs([]);
(log, search)
def wait() & finished() = reply to wait
let register name service = Join.Ns.register Join.Ns.here name service
let () =
let log, search = create_logger () in
register "log" log;
register "search" search;
Join.Site.listen (Unix.ADDR_INET (Join.Site.get_local_addr(), 12345));
wait () |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Icon_and_Unicon | Icon and Unicon |
procedure main(A)
host := gethost( A[1] | "www.kame.net") | stop("can't translate")
write(host.name, ": ", host.addresses)
end
|
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #J | J | 2!:0'dig -4 +short www.kame.net'
orange.kame.net.
203.178.141.194
2!:0'dig -6 +short www.kame.net'
|interface error
| 2!:0'dig -6 +short www.kame.net' |
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #PicoLisp | PicoLisp | # Need some turtle graphics
(load "@lib/math.l")
(setq
*TurtleX 100 # X position
*TurtleY 75 # Y position
*TurtleA 0.0 ) # Angle
(de fd (Img Len) # Forward
(let (R (*/ *TurtleA pi 180.0) DX (*/ (cos R) Len 1.0) DY (*/ (sin R) Len 1.0))
(brez Img *TurtleX *TurtleY DX DY)
(inc '*TurtleX DX)
(inc '*TurtleY DY) ) )
(de rt (A) # Right turn
(inc '*TurtleA A) )
(de lt (A) # Left turn
(dec '*TurtleA A) )
# Dragon curve stuff
(de *DragonStep . 4)
(de dragon (Img Depth Dir)
(if (=0 Depth)
(fd Img *DragonStep)
(rt Dir)
(dragon Img (dec Depth) 45.0)
(lt (* 2 Dir))
(dragon Img (dec Depth) -45.0)
(rt Dir) ) )
# Run it
(let Img (make (do 200 (link (need 300 0)))) # Create image 300 x 200
(dragon Img 10 45.0) # Build dragon curve
(out "img.pbm" # Write to bitmap file
(prinl "P1")
(prinl 300 " " 200)
(mapc prinl Img) ) ) |
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #J | J | fourbanger=:3 :0
e=. ('e(',')',~])@":&.> 1+i.#y
firstpos=. 0< {.y-.0
if. */0=y do. '0' else. firstpos}.;y gluedto e end.
)
gluedto=:4 :0 each
pfx=. '+-' {~ x<0
select. |x
case. 0 do. ''
case. 1 do. pfx,y
case. do. pfx,(":|x),'*',y
end.
) |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Logtalk | Logtalk |
:- object(set(_Type),
extends(set)).
% the info/1 directive is the main directive for documenting an entity
% its value is a list of Key-Value pairs; the set of keys is user-extendable
:- info([
version is 1.2,
author is 'A. Coder',
date is 2013/10/13,
comment is 'Set predicates with elements constrained to a single type.',
parnames is ['Type']
]).
% the info/2 directive is the main directive for documenting predicates
% its second value is a list of Key-Value pairs; the set of keys is user-extendable
:- public(intersection/3).
:- mode(intersection(+set, +set, ?set), zero_or_one).
:- info(intersection/3, [
comment is 'Returns the intersection of Set1 and Set2.',
argnames is ['Set1', 'Set2', 'Intersection']
]).
...
:- end_object.
|
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Lua | Lua | --- Converts degrees to radians (summary).
-- Given an angle measure in degrees, return an equivalent angle measure in radians (long description).
-- @param deg the angle measure in degrees
-- @return the angle measure in radians
-- @see rad2deg
function deg2rad(deg) return deg*math.pi/180 end |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #Jsish | Jsish | /* Diverisity Prediction Theorem, in Jsish */
"use strict";
function sum(arr:array):number {
return arr.reduce(function(acc, cur, idx, arr) { return acc + cur; });
}
function square(x:number):number {
return x * x;
}
function mean(arr:array):number {
return sum(arr) / arr.length;
}
function averageSquareDiff(a:number, predictions:array):number {
return mean(predictions.map(function(x:number):number { return square(x - a); }));
}
function diversityTheorem(truth:number, predictions:array):object {
var average = mean(predictions);
return {
"average-error": averageSquareDiff(truth, predictions),
"crowd-error": square(truth - average),
"diversity": averageSquareDiff(average, predictions)
};
}
;diversityTheorem(49, [48,47,51]);
;diversityTheorem(49, [48,47,51,42]);
/*
=!EXPECTSTART!=
diversityTheorem(49, [48,47,51]) ==> { "average-error":3, "crowd-error":0.1111111111111127, diversity:2.888888888888889 }
diversityTheorem(49, [48,47,51,42]) ==> { "average-error":14.5, "crowd-error":4, diversity:10.5 }
=!EXPECTEND!=
*/ |
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #LaTeX | LaTeX | \documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{shadings}
\begin{document}
\begin{tikzpicture}
\shade[ball color=black] (0,0) circle (4);
\end{tikzpicture}
\end{document} |
http://rosettacode.org/wiki/Doubly-linked_list/Definition | Doubly-linked list/Definition | Define the data structure for a complete Doubly Linked List.
The structure should support adding elements to the head, tail and middle of the list.
The structure should not allow circular loops
See also
Array
Associative array: Creation, Iteration
Collections
Compound data type
Doubly-linked list: Definition, Element definition, Element insertion, List Traversal, Element Removal
Linked list
Queue: Definition, Usage
Set
Singly-linked list: Element definition, Element insertion, List Traversal, Element Removal
Stack
| #ATS | ATS | (********************************************************************)
(* The public interface *)
abstype dllist_t (t : t@ype+, is_root : bool) (* An abstract type. *)
typedef dllist_t (t : t@ype+) = [b : bool] dllist_t (t, b)
(* Make a new dllist_t, consisting of a root node. *)
fun {t : t@ype}
dllist_t_make () : dllist_t (t, true)
(* Is this the root node, with no element stored? *)
fun {t : t@ype}
dllist_t_is_root
{is_root : bool}
(dl : dllist_t (t, is_root)) :
[b : bool | b == is_root]
bool b
(* Is this a non-root node, with an element stored? *)
fun {t : t@ype}
dllist_t_isnot_root
{is_root : bool}
(dl : dllist_t (t, is_root)) :
[b : bool | b == ~is_root]
bool b
(* Return the root node of the list. *)
fun {t : t@ype}
dllist_t_root (dl : dllist_t t) : dllist_t (t, true)
(* Return the previous node. *)
fun {t : t@ype}
dllist_t_previous (dl : dllist_t t) : dllist_t t
(* Return the next node. *)
fun {t : t@ype}
dllist_t_next (dl : dllist_t t) : dllist_t t
(* Insert an element before the given node. *)
fun {t : t@ype}
dllist_t_insert_before (dl : dllist_t t, elem : t) : void
(* Insert an element after the given node. *)
fun {t : t@ype}
dllist_t_insert_after (dl : dllist_t t, elem : t) : void
(* Remove the given node. It is an error to call this on the root
node. *)
fun {t : t@ype}
dllist_t_remove (dl : dllist_t t) : void
(* Return a copy of the stored element. It is an error to call this on
the root node. *)
fun {t : t@ype}
dllist_t_element (dl: dllist_t t) : t
fun {t : t@ype}
dllist_t_make_generator (dl: dllist_t t, direction : int) :
() -<cloref1> Option t
fun {t : t@ype}
dllist_t_to_list
(dl : dllist_t t) : [n : nat] list (t, n)
fun {t : t@ype}
list_to_dllist_t
{n : int}
(dl : list (t, n)) : dllist_t t
(********************************************************************) |
http://rosettacode.org/wiki/Display_an_outline_as_a_nested_table | Display an outline as a nested table |
Display an outline as a nested table.
Parse the outline to a tree,
count the leaves descending from each node,
and write out a table with 'colspan' values
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
defining the width of a leaf as 1,
and the width of a parent node as a sum.
either as a wiki table,
or as HTML.
(The sum of the widths of its children)
The graphic representation of outlines is a staple of mind-mapping and the planning of papers, reports, and speeches.
Task
Given a outline with at least 3 levels of indentation, for example:
Display an outline as a nested table.
Parse the outline to a tree,
measuring the indent of each line,
translating the indentation to a nested structure,
and padding the tree to even depth.
count the leaves descending from each node,
defining the width of a leaf as 1,
and the width of a parent node as a sum.
(The sum of the widths of its children)
and write out a table with 'colspan' values
either as a wiki table,
or as HTML.
write a program in your language which translates your outline into a nested table, with WikiTable or HTML colspan values attached (where needed) to parent nodes in the nested table.
The WikiTable at the top of this page was generated from the indented outline shown above, producing the following markup string:
{| class="wikitable" style="text-align: center;"
|-
| style="background: #ffffe6; " colspan=7 | Display an outline as a nested table.
|-
| style="background: #ffebd2; " colspan=3 | Parse the outline to a tree,
| style="background: #f0fff0; " colspan=2 | count the leaves descending from each node,
| style="background: #e6ffff; " colspan=2 | and write out a table with 'colspan' values
|-
| style="background: #ffebd2; " | measuring the indent of each line,
| style="background: #ffebd2; " | translating the indentation to a nested structure,
| style="background: #ffebd2; " | and padding the tree to even depth.
| style="background: #f0fff0; " | defining the width of a leaf as 1,
| style="background: #f0fff0; " | and the width of a parent node as a sum.
| style="background: #e6ffff; " | either as a wiki table,
| style="background: #e6ffff; " | or as HTML.
|-
| |
| |
| |
| |
| style="background: #f0fff0; " | (The sum of the widths of its children)
| |
| |
|}
Extra credit
Use background color to distinguish the main stages of your outline, so that the subtree of each node at level two is consistently colored, and the edges between adjacent subtrees are immediately revealed.
Output
Display your nested table on this page.
| #Python | Python | """Display an outline as a nested table. Requires Python >=3.6."""
import itertools
import re
import sys
from collections import deque
from typing import NamedTuple
RE_OUTLINE = re.compile(r"^((?: |\t)*)(.+)$", re.M)
COLORS = itertools.cycle(
[
"#ffffe6",
"#ffebd2",
"#f0fff0",
"#e6ffff",
"#ffeeff",
]
)
class Node:
def __init__(self, indent, value, parent, children=None):
self.indent = indent
self.value = value
self.parent = parent
self.children = children or []
self.color = None
def depth(self):
if self.parent:
return self.parent.depth() + 1
return -1
def height(self):
"""Height of the subtree rooted at this node."""
if not self.children:
return 0
return max(child.height() for child in self.children) + 1
def colspan(self):
if self.leaf:
return 1
return sum(child.colspan() for child in self.children)
@property
def leaf(self):
return not bool(self.children)
def __iter__(self):
# Level order tree traversal.
q = deque()
q.append(self)
while q:
node = q.popleft()
yield node
q.extend(node.children)
class Token(NamedTuple):
indent: int
value: str
def tokenize(outline):
"""Generate ``Token``s from the given outline."""
for match in RE_OUTLINE.finditer(outline):
indent, value = match.groups()
yield Token(len(indent), value)
def parse(outline):
"""Return the given outline as a tree of ``Node``s."""
# Split the outline into lines and count the level of indentation.
tokens = list(tokenize(outline))
# Parse the tokens into a tree of nodes.
temp_root = Node(-1, "", None)
_parse(tokens, 0, temp_root)
# Pad the tree so that all branches have the same depth.
root = temp_root.children[0]
pad_tree(root, root.height())
return root
def _parse(tokens, index, node):
"""Recursively build a tree of nodes.
Args:
tokens (list): A collection of ``Token``s.
index (int): Index of the current token.
node (Node): Potential parent or sibling node.
"""
# Base case. No more lines.
if index >= len(tokens):
return
token = tokens[index]
if token.indent == node.indent:
# A sibling of node
current = Node(token.indent, token.value, node.parent)
node.parent.children.append(current)
_parse(tokens, index + 1, current)
elif token.indent > node.indent:
# A child of node
current = Node(token.indent, token.value, node)
node.children.append(current)
_parse(tokens, index + 1, current)
elif token.indent < node.indent:
# Try the node's parent until we find a sibling.
_parse(tokens, index, node.parent)
def pad_tree(node, height):
"""Pad the tree with blank nodes so all branches have the same depth."""
if node.leaf and node.depth() < height:
pad_node = Node(node.indent + 1, "", node)
node.children.append(pad_node)
for child in node.children:
pad_tree(child, height)
def color_tree(node):
"""Walk the tree and color each node as we go."""
if not node.value:
node.color = "#F9F9F9"
elif node.depth() <= 1:
node.color = next(COLORS)
else:
node.color = node.parent.color
for child in node.children:
color_tree(child)
def table_data(node):
"""Return an HTML table data element for the given node."""
indent = " "
if node.colspan() > 1:
colspan = f'colspan="{node.colspan()}"'
else:
colspan = ""
if node.color:
style = f'style="background-color: {node.color};"'
else:
style = ""
attrs = " ".join([colspan, style])
return f"{indent}<td{attrs}>{node.value}</td>"
def html_table(tree):
"""Return the tree as an HTML table."""
# Number of columns in the table.
table_cols = tree.colspan()
# Running count of columns in the current row.
row_cols = 0
# HTML buffer
buf = ["<table style='text-align: center;'>"]
# Breadth first iteration.
for node in tree:
if row_cols == 0:
buf.append(" <tr>")
buf.append(table_data(node))
row_cols += node.colspan()
if row_cols == table_cols:
buf.append(" </tr>")
row_cols = 0
buf.append("</table>")
return "\n".join(buf)
def wiki_table_data(node):
"""Return an wiki table data string for the given node."""
if not node.value:
return "| |"
if node.colspan() > 1:
colspan = f"colspan={node.colspan()}"
else:
colspan = ""
if node.color:
style = f'style="background: {node.color};"'
else:
style = ""
attrs = " ".join([colspan, style])
return f"| {attrs} | {node.value}"
def wiki_table(tree):
"""Return the tree as a wiki table."""
# Number of columns in the table.
table_cols = tree.colspan()
# Running count of columns in the current row.
row_cols = 0
# HTML buffer
buf = ['{| class="wikitable" style="text-align: center;"']
for node in tree:
if row_cols == 0:
buf.append("|-")
buf.append(wiki_table_data(node))
row_cols += node.colspan()
if row_cols == table_cols:
row_cols = 0
buf.append("|}")
return "\n".join(buf)
def example(table_format="wiki"):
"""Write an example table to stdout in either HTML or Wiki format."""
outline = (
"Display an outline as a nested table.\n"
" Parse the outline to a tree,\n"
" measuring the indent of each line,\n"
" translating the indentation to a nested structure,\n"
" and padding the tree to even depth.\n"
" count the leaves descending from each node,\n"
" defining the width of a leaf as 1,\n"
" and the width of a parent node as a sum.\n"
" (The sum of the widths of its children)\n"
" and write out a table with 'colspan' values\n"
" either as a wiki table,\n"
" or as HTML."
)
tree = parse(outline)
color_tree(tree)
if table_format == "wiki":
print(wiki_table(tree))
else:
print(html_table(tree))
if __name__ == "__main__":
args = sys.argv[1:]
if len(args) == 1:
table_format = args[0]
else:
table_format = "wiki"
example(table_format) |
http://rosettacode.org/wiki/Draw_a_clock | Draw a clock | Task
Draw a clock.
More specific:
Draw a time keeping device. It can be a stopwatch, hourglass, sundial, a mouth counting "one thousand and one", anything. Only showing the seconds is required, e.g.: a watch with just a second hand will suffice. However, it must clearly change every second, and the change must cycle every so often (one minute, 30 seconds, etc.) It must be drawn; printing a string of numbers to your terminal doesn't qualify. Both text-based and graphical drawing are OK.
The clock is unlikely to be used to control space flights, so it needs not be hyper-accurate, but it should be usable, meaning if one can read the seconds off the clock, it must agree with the system clock.
A clock is rarely (never?) a major application: don't be a CPU hog and poll the system timer every microsecond, use a proper timer/signal/event from your system or language instead. For a bad example, many OpenGL programs update the frame-buffer in a busy loop even if no redraw is needed, which is very undesirable for this task.
A clock is rarely (never?) a major application: try to keep your code simple and to the point. Don't write something too elaborate or convoluted, instead do whatever is natural, concise and clear in your language.
Key points
animate simple object
timed event
polling system resources
code clarity
| #Wren | Wren | import "graphics" for Canvas, Color
import "dome" for Window
import "math" for Math
var Degrees06 = Num.pi / 30
var Degrees30 = Degrees06 * 5
var Degrees90 = Degrees30 * 3
class Clock {
construct new(hour, minute, second) {
Window.title = "Clock"
_size = 590
Window.resize(_size, _size)
Canvas.resize(_size, _size)
_spacing = 40
_diameter = _size - 2 * _spacing
_cx = (_diameter / 2).floor + _spacing
_cy = _cx
_hour = hour
_minute = minute
_second = second
}
drawFace() {
var radius = (_diameter / 2).floor
Canvas.circlefill(_cx, _cy, radius, Color.yellow)
Canvas.circle(_cx, _cy, radius, Color.black)
}
drawHand(angle, radius, color) {
var x = _cx + (radius * Math.cos(angle)).truncate
var y = _cy - (radius * Math.sin(angle)).truncate
Canvas.line(_cx, _cy, x, y, color, 2)
}
drawClock() {
Canvas.cls(Color.white)
drawFace()
var angle = Degrees90 - Degrees06 * _second
drawHand(angle, (_diameter/2).floor - 30, Color.red)
var minsecs = _minute + _second/60
angle = Degrees90 - Degrees06 * minsecs
drawHand(angle, (_diameter / 3).floor + 10, Color.black)
var hourmins = _hour + minsecs / 60
angle = Degrees90 - Degrees30 * hourmins
drawHand(angle, (_diameter / 4).floor + 10, Color.black)
}
init() {
_frame = 0
drawClock()
}
update() {
_frame = _frame + 1
if (_frame == 60) {
_frame = 0
_second = _second + 1
if (_second == 60) {
_minute = _minute + 1
_second = 0
if (_minute == 60) {
_hour = _hour + 1
_minute = 0
if (_hour == 24) _hour = 0
}
}
}
}
draw(alpha) {
drawClock()
}
}
var Game = Clock.new(0, 0, 0) // start at midnight |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Oz | Oz | declare
functor ServerCode
export
port:Prt
define
Stream
Prt = {NewPort ?Stream}
thread
for Request#Reply in Stream do
case Request
of echo(Data) then Reply = Data
[] compute(Function) then Reply = {Function}
end
end
end
end
%% create the server on some machine
%% (just change "localhost" to some machine
%% that you can use with a passwordless rsh login
%% and that has the same Mozart version installed)
RM = {New Remote.manager init(host:localhost)}
%% execute the code encapsulated in the ServerCode functor
Server = {RM apply(ServerCode $)}
%% Shortcut: send a message to Server and receive a reply
fun {Send X}
{Port.sendRecv Server.port X}
end
in
%% echo
{System.showInfo "Echo reply: "#{Send echo(hello)}}
%% compute
{System.showInfo "Result of computation: "#
{Send compute(fun {$} 8 div 4 end)}}
%% shut down server
{RM close} |
http://rosettacode.org/wiki/Distributed_programming | Distributed programming | Write two programs (or one program with two modes) which run on networked computers, and send some messages between them.
The protocol used may be language-specific or not, and should be suitable for general distributed programming; that is, the protocol should be generic (not designed just for the particular example application), readily capable of handling the independent communications of many different components of a single application, and the transferring of arbitrary data structures natural for the language.
This task is intended to demonstrate high-level communication facilities beyond just creating sockets.
| #Perl | Perl | use Data::Dumper;
use IO::Socket::INET;
use Safe;
sub get_data {
my $sock = new IO::Socket::INET
LocalHost => "localhost",
LocalPort => "10000",
Proto => "tcp",
Listen => 1,
Reuse => 1;
unless ($sock) { die "Socket creation failure" }
my $cli = $sock->accept();
# of course someone may be tempted to send you 'system("rm -rf /")',
# to be safe(r), use Safe::
my $safe = new Safe;
my $x = $safe->reval(join("", <$cli>));
close $cli;
close $sock;
return $x;
}
sub send_data {
my $host = shift;
my $data = shift;
my $sock = new IO::Socket::INET
PeerAddr => "$host:10000",
Proto => "tcp",
Reuse => 1;
unless ($sock) { die "Socket creation failure" }
print $sock Data::Dumper->Dump([$data]);
close $sock;
}
if (@ARGV) {
my $x = get_data();
print "Got data\n", Data::Dumper->Dump([$x]);
} else {
send_data('some_host', { a=>100, b=>[1 .. 10] });
} |
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #Java | Java | import java.net.InetAddress;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.UnknownHostException;
class DnsQuery {
public static void main(String[] args) {
try {
InetAddress[] ipAddr = InetAddress.getAllByName("www.kame.net");
for(int i=0; i < ipAddr.length ; i++) {
if (ipAddr[i] instanceof Inet4Address) {
System.out.println("IPv4 : " + ipAddr[i].getHostAddress());
} else if (ipAddr[i] instanceof Inet6Address) {
System.out.println("IPv6 : " + ipAddr[i].getHostAddress());
}
}
} catch (UnknownHostException uhe) {
System.err.println("unknown host");
}
}
}
|
http://rosettacode.org/wiki/DNS_query | DNS query | DNS is an internet service that maps domain names, like rosettacode.org, to IP addresses, like 66.220.0.231.
Use DNS to resolve www.kame.net to both IPv4 and IPv6 addresses. Print these addresses.
| #JavaScript | JavaScript | const dns = require("dns");
dns.lookup("www.kame.net", {
all: true
}, (err, addresses) => {
if(err) return console.error(err);
console.log(addresses);
})
|
http://rosettacode.org/wiki/Dragon_curve | Dragon curve |
Create and display a dragon curve fractal.
(You may either display the curve directly or write it to an image file.)
Algorithms
Here are some brief notes the algorithms used and how they might suit various languages.
Recursively a right curling dragon is a right dragon followed by a left dragon, at 90-degree angle. And a left dragon is a left followed by a right.
*---R----* expands to * *
\ /
R L
\ /
*
*
/ \
L R
/ \
*---L---* expands to * *
The co-routines dcl and dcr in various examples do this recursively to a desired expansion level.
The curl direction right or left can be a parameter instead of two separate routines.
Recursively, a curl direction can be eliminated by noting the dragon consists of two copies of itself drawn towards a central point at 45-degrees.
*------->* becomes * * Recursive copies drawn
\ / from the ends towards
\ / the centre.
v v
*
This can be seen in the SVG example. This is best suited to off-line drawing since the reversal in the second half means the drawing jumps backward and forward (in binary reflected Gray code order) which is not very good for a plotter or for drawing progressively on screen.
Successive approximation repeatedly re-writes each straight line as two new segments at a right angle,
*
*-----* becomes / \ bend to left
/ \ if N odd
* *
* *
*-----* becomes \ / bend to right
\ / if N even
*
Numbering from the start of the curve built so far, if the segment is at an odd position then the bend introduced is on the right side. If the segment is an even position then on the left. The process is then repeated on the new doubled list of segments. This constructs a full set of line segments before any drawing.
The effect of the splitting is a kind of bottom-up version of the recursions. See the Asymptote example for code doing this.
Iteratively the curve always turns 90-degrees left or right at each point. The direction of the turn is given by the bit above the lowest 1-bit of n. Some bit-twiddling can extract that efficiently.
n = 1010110000
^
bit above lowest 1-bit, turn left or right as 0 or 1
LowMask = n BITXOR (n-1) # eg. giving 0000011111
AboveMask = LowMask + 1 # eg. giving 0000100000
BitAboveLowestOne = n BITAND AboveMask
The first turn is at n=1, so reckon the curve starting at the origin as n=0 then a straight line segment to position n=1 and turn there.
If you prefer to reckon the first turn as n=0 then take the bit above the lowest 0-bit instead. This works because "...10000" minus 1 is "...01111" so the lowest 0 in n-1 is where the lowest 1 in n is.
Going by turns suits turtle graphics such as Logo or a plotter drawing with a pen and current direction.
If a language doesn't maintain a "current direction" for drawing then you can always keep that separately and apply turns by bit-above-lowest-1.
Absolute direction to move at point n can be calculated by the number of bit-transitions in n.
n = 11 00 1111 0 1
^ ^ ^ ^ 4 places where change bit value
so direction=4*90degrees=East
This can be calculated by counting the number of 1 bits in "n XOR (n RIGHTSHIFT 1)" since such a shift and xor leaves a single 1 bit at each position where two adjacent bits differ.
Absolute X,Y coordinates of a point n can be calculated in complex numbers by some powers (i+1)^k and add/subtract/rotate. This is done in the gnuplot code. This might suit things similar to Gnuplot which want to calculate each point independently.
Predicate test for whether a given X,Y point or segment is on the curve can be done. This might suit line-by-line output rather than building an entire image before printing. See M4 for an example of this.
A predicate works by dividing out complex number i+1 until reaching the origin, so it takes roughly a bit at a time from X and Y is thus quite efficient. Why it works is slightly subtle but the calculation is not difficult. (Check segment by applying an offset to move X,Y to an "even" position before dividing i+1. Check vertex by whether the segment either East or West is on the curve.)
The number of steps in the predicate corresponds to doublings of the curve, so stopping the check at say 8 steps can limit the curve drawn to 2^8=256 points. The offsets arising in the predicate are bits of n the segment number, so can note those bits to calculate n and limit to an arbitrary desired length or sub-section.
As a Lindenmayer system of expansions. The simplest is two symbols F and S both straight lines, as used by the PGF code.
Axiom F, angle 90 degrees
F -> F+S
S -> F-S
This always has F at even positions and S at odd. Eg. after 3 levels F_S_F_S_F_S_F_S. The +/- turns in between bend to the left or right the same as the "successive approximation" method above. Read more at for instance Joel Castellanos' L-system page.
Variations are possible if you have only a single symbol for line draw, for example the Icon and Unicon and Xfractint code. The angles can also be broken into 45-degree parts to keep the expansion in a single direction rather than the endpoint rotating around.
The string rewrites can be done recursively without building the whole string, just follow its instructions at the target level. See for example C by IFS Drawing code. The effect is the same as "recursive with parameter" above but can draw other curves defined by L-systems.
| #PL.2FI | PL/I |
* PROCESS GONUMBER, MARGINS(1,72), NOINTERRUPT, MACRO;
TEST:PROCEDURE OPTIONS(MAIN);
DECLARE
SYSIN FILE STREAM INPUT,
DRAGON FILE STREAM OUTPUT PRINT,
SYSPRINT FILE STREAM OUTPUT PRINT;
DECLARE (MIN,MAX,MOD,INDEX,LENGTH,SUBSTR,VERIFY,TRANSLATE) BUILTIN;
DECLARE (COMPLEX,SQRT,REAL,IMAG,ATAN,SIN,EXP,COS,ABS) BUILTIN;
%INCLUDE PLILIB(GOODIES);
%INCLUDE PLILIB(SCAN);
%INCLUDE PLILIB(GRAMMAR);
%INCLUDE PLILIB(CARDINAL);
%INCLUDE PLILIB(ORDINAL);
%INCLUDE PLILIB(ANSWAROD);
%INCLUDE PLILIB(RUNFILE);
%INCLUDE PLILIB(PSTUFF);
DECLARE (TWOPI,TORAD) REAL;
DECLARE RANGE(4) REAL;
DECLARE TRACERANGE BOOLEAN INITIAL(FALSE);
DECLARE FRESHRANGE BOOLEAN INITIAL(TRUE);
BOUND:PROCEDURE(Z);
DECLARE Z COMPLEX;
DECLARE (ZX,ZY) REAL;
ZX = REAL(Z); ZY = IMAG(Z);
IF FRESHRANGE THEN
DO;
RANGE(1),RANGE(2) = ZX;
RANGE(3),RANGE(4) = ZY;
END;
ELSE
DO;
RANGE(1) = MIN(RANGE(1),ZX);
RANGE(2) = MAX(RANGE(2),ZX);
RANGE(3) = MIN(RANGE(3),ZY);
RANGE(4) = MAX(RANGE(4),ZY);
END;
FRESHRANGE = FALSE;
END BOUND;
PLOTZ:PROCEDURE(Z,PEN);
DECLARE Z COMPLEX;
DECLARE PEN INTEGER;
IF TRACERANGE THEN CALL BOUND(Z);
CALL PLOT(REAL(Z),IMAG(Z),PEN);
END PLOTZ;
%PAGE;
DRAGONCURVE:PROCEDURE(ORDER,HOP); /*Folding paper in two...*/
/*Some statistics on runs with x = 56.25", y = 32.6"
&(the calcomp plotter).*/
/*The actual size of the picture determines the number of steps
&to each quarter-turn.*/
/* n turns x y secs dx dy
&*/
/* 20 1,048,575 -2389:681 -682:1364 180+ 3070 2046
&*/
/* 19 524,287 -1365:681 -340:1364 119 2046 1704
&*/
/* 18 262,143 -341:681 -340:1194 71 1022 1554
&*/
/* 17 131,071 -171:681 -340:682 35 852 1022
&*/
DECLARE ORDER BIGINT; /*So how many folds.*/
DECLARE HOP BOOLEAN;
DECLARE FOLD(0:31,0:32767) BOOLEAN; /*Oh for (0:1000000) or so..*/
DECLARE (TURN,N,IT,I,I1,I2,J1,J2,L,LL) BIGINT;
DECLARE (XMIN,XMAX,YMIN,YMAX,XMID,YMID) REAL;
DECLARE (IXMIN,IXMAX,IYMIN,IYMAX) BIGINT;
DECLARE (S,H,TORAD) REAL;
DECLARE (ZMID,Z,Z2,DZ,ZL) COMPLEX;
DECLARE (FULLTURN,ABOUTTURN,QUARTERTURN) INTEGER;
DECLARE (WAY,DIRECTION,ND,LD,LD1,LD2) INTEGER;
DECLARE LEAF(0:3,0:360) COMPLEX; /*Corner turning.*/
DECLARE SWAPXY BOOLEAN; /*Try to align rectangles.*/
DECLARE (T1,T2) CHARACTER(200) VARYING;
IF ¬PLOTCHOICE('') THEN RETURN; /*Ascertain the plot device.*/
N = 0;
FOR TURN = 1 TO ORDER;
IT = N + 1;
I1 = IT/32768; I2 = MOD(IT,32768);
FOLD(I1,I2) = TRUE;
FOR I = 1 TO N;
I1 = (IT + I)/32768; I2 = MOD(IT + I,32768);
J1 = (IT - I)/32768; J2 = MOD(IT - I,32768);
FOLD(I1,I2) = ¬FOLD(J1,J2);
END;
N = N*2 + 1;
IF HOP & TURN < ORDER THEN GO TO XX;
XMIN,XMAX,YMIN,YMAX = 0;
Z = 0; /*Start at the origin.*/
DZ = 1; /*Step out unilaterally.*/
FOR I = 1 TO N;
Z = Z + DZ; /*Take the step before the kink.*/
I1 = I/32768; I2 = MOD(I,32768);
IF FOLD(I1,I2) THEN DZ = DZ*(0 + 1I); ELSE DZ = DZ*(0 - 1I);
Z = Z + DZ; /*The step after the kink.*/
XMIN = MIN(XMIN,REAL(Z)); XMAX = MAX(XMAX,REAL(Z));
YMIN = MIN(YMIN,IMAG(Z)); YMAX = MAX(YMAX,IMAG(Z));
END;
SWAPXY = ((XMAX - XMIN) >= (YMAX - YMIN)) /*Contemplate */
¬= (PLOTSTUFF.XSIZE >= PLOTSTUFF.YSIZE); /* rectangularities.*/
IF SWAPXY THEN
DO;
H = XMIN;
XMIN = YMIN;
YMIN = -XMAX;
XMAX = YMAX;
YMAX = -H;
END;
IXMAX = XMAX; IYMAX = YMAX; IXMIN = XMIN; IYMIN = YMIN;
XMID = (XMAX + XMIN)/2; YMID = (YMAX + YMIN)/2;
ZMID = COMPLEX(XMID,YMID);
XMAX = XMAX - XMID; YMAX = YMAX - YMID;
XMIN = XMIN - XMID; YMIN = YMIN - YMID;
T1 = 'Order ' || IFMT(TURN) || ' Dragoncurve, '
|| SAYNUM(0,N,'turn') || '.';
IF SWAPXY THEN T2 = 'y range ' || IFMT(IYMIN) || ':' || IFMT(IYMAX)
|| ', x range ' || IFMT(IXMIN) || ':' || IFMT(IXMAX);
ELSE T2 = 'x range ' || IFMT(IXMIN) || ':' || IFMT(IXMAX)
|| ', y range ' || IFMT(IYMIN) || ':' || IFMT(IYMAX);
S = MIN(PLOTSTUFF.XSIZE/(XMAX - XMIN), /*Rectangularity */
(PLOTSTUFF.YSIZE - 4*H)/(YMAX - YMIN)); /* matching?*/
H = MIN(PLOTSTUFF.XSIZE,S*(XMAX - XMIN)); /*X-width for text.*/
H = MIN(PLOTCHAR,H/(MAX(LENGTH(T1),LENGTH(T2)) + 6));
IF ¬NEWRANGE(XMIN*S,XMAX*S,YMIN*S-2*H,YMAX*S+2*H) THEN STOP('Urp!');
CALL PLOTTEXT(-LENGTH(T1)*H/2,YMAX*S + 2*PLOTTICK,H,T1,0);
CALL PLOTTEXT(-LENGTH(T2)*H/2,YMIN*S - 2*H + 2*PLOTTICK,H,T2,0);
QUARTERTURN = MIN(MAX(3,12*SQRT(S)),90); /*Angle refinement.*/
ABOUTTURN = QUARTERTURN*2;
FULLTURN = QUARTERTURN*4; /*Ensures divisibility.*/
TORAD = TWOPI/FULLTURN; /*Imagine if FULLTURN was 360.*/
ZL = 1; /*Start with 0 degrees.*/
FOR L = 0 TO 3; /*The four directions.*/
FOR I = 0 TO FULLTURN; /*Fill out the petals in the corner.*/
LEAF(L,I) = ZL + EXP((0 + 1I)*I*TORAD); /*Poke!*/
END; /*Fill out the full circle for each for simplicity.*/
ZL = ZL*(0 + 1I); /*Rotate to the next axis.*/
END; /*Four circles, centred one unit along each axial direction.*/
Z = -ZMID; /*The start point. Was 0, before shift by ZMID.*/
CALL PLOTZ(S*Z,3); /*Position the pen.*/
DIRECTION = 0; /*The way ahead is along the x-axis.*/
DZ = 1; /*The step before the kink.*/
IF SWAPXY THEN DIRECTION = -QUARTERTURN; /*Or maybe y.*/
IF SWAPXY THEN DZ = (0 - 1I); /*An x-y swap.*/
FRESHRANGE = TRUE; /*A sniffing.*/
FOR I = 1 TO N; /*The deviationism begins.*/
I1 = I/32768; I2 = MOD(I,32768);
IF FOLD(I1,I2) THEN WAY = +1; ELSE WAY = -1;
ND = DIRECTION + QUARTERTURN*WAY;
IF ND >= FULLTURN THEN ND = ND - FULLTURN;
IF ND < 0 THEN ND = ND + FULLTURN;
LD = ND/QUARTERTURN; /*Select a leaf.*/
LD1 = MOD(ND + ABOUTTURN,FULLTURN);
LD2 = LD1 + WAY*QUARTERTURN; /*No mod, see the FOR loop below.*/
FOR L = LD1 TO LD2 BY WAY; /*Round the kink.*/
LL = L; /*A copy to wrap into range.*/
IF LL < 0 THEN LL = LL + FULLTURN;
IF LL >= FULLTURN THEN LL = LL - FULLTURN;
ZL = Z + LEAF(LD,LL); /*Work along the curve.*/
CALL PLOTZ(S*ZL,2); /*Move a bit.*/
END; /*On to the next step.*/
DIRECTION = ND; /*The new direction.*/
Z = Z + DZ; /*The first half of the step that has been rounded.*/
DZ = DZ*(0 + 1I)*WAY; /*A right-angle, one way or the other.*/
Z = Z + DZ; /*Avoid the roundoff of hordes of fractional moves.*/
END; /*On to the next fold.*/
CALL PLOT(0,0,998);
IF TRACERANGE THEN PUT SKIP(3) FILE(DRAGON) LIST('Dragoncurve: ');
IF TRACERANGE THEN PUT FILE(DRAGON) DATA(RANGE,ORDER,S,ZMID);
XX:END;
END DRAGONCURVE;
%PAGE;
%PAGE;
%PAGE;
RANDOM:PROCEDURE(SEED) RETURNS(REAL);
DECLARE SEED INTEGER;
SEED = SEED*497 + 4032;
IF SEED <= 0 THEN SEED = SEED + 32767;
IF SEED > 32767 THEN SEED = MOD(SEED,32767);
RETURN(SEED/32767.0);
END RANDOM;
%PAGE;
TRACE:PROCEDURE(O,R,A,N,G);
DECLARE (I,N,G) INTEGER;
DECLARE (O,R,A(*),X0,X1,X2) COMPLEX;
X1 = O + R*A(1);
X0 = X1;
CALL PLOT(REAL(X1),IMAG(X1),3);
FOR I = 2 TO N;
X2 = O + R*A(I);
CALL PLOT(REAL(X2),IMAG(X2),2);
X1 = X2;
END;
CALL PLOT(REAL(X0),IMAG(X0),2);
END TRACE;
CENTREZ:PROCEDURE(A,N);
DECLARE (A(*),T) COMPLEX;
DECLARE (I,N) INTEGER;
T = 0;
FOR I = 1 TO N;
T = T + A(I);
END;
T = T/N;
FOR I = 1 TO N;
A(I) = A(I) - T;
END;
END CENTREZ;
%PAGE;
%PAGE;
DECLARE (BELCH,ORDER,CHASE,TWIRL) INTEGER;
DECLARE HOP BOOLEAN;
TWOPI = 8*ATAN(1);
TORAD = TWOPI/360;
BELCH = REPLYN('How many dragoncurves (max 20)');
IF BELCH < 12 THEN HOP = FALSE;
ELSE HOP = YEA('Go directly to order ' || IFMT(BELCH));
/*ORDER = REPLYN('The depth of recursion (eg 4)');
CHASE = REPLYN('How many pursuits');
TWIRL = REPLYN('How many twirls');
TRACERANGE = YEA('Trace the ranges');*/
CALL DRAGONCURVE(BELCH,HOP);
/*CALL TRIANGLEPLEX(ORDER);
CALL SQUAREBASH(ORDER,+1);
CALL SQUAREBASH(ORDER,-1);
CALL SNOWFLAKE(ORDER);
CALL SNOWFLAKE3(ORDER);
CALL PURSUE(CHASE);
CALL LISSAJOU(TWIRL);
CALL CARDIOD;
CALL HEART;*/
CALL PLOT(0,0,-3); CALL PLOT(0,0,999);
END TEST;
|
http://rosettacode.org/wiki/Display_a_linear_combination | Display a linear combination | Task
Display a finite linear combination in an infinite vector basis
(
e
1
,
e
2
,
…
)
{\displaystyle (e_{1},e_{2},\ldots )}
.
Write a function that, when given a finite list of scalars
(
α
1
,
α
2
,
…
)
{\displaystyle (\alpha ^{1},\alpha ^{2},\ldots )}
,
creates a string representing the linear combination
∑
i
α
i
e
i
{\displaystyle \sum _{i}\alpha ^{i}e_{i}}
in an explicit format often used in mathematics, that is:
α
i
1
e
i
1
±
|
α
i
2
|
e
i
2
±
|
α
i
3
|
e
i
3
±
…
{\displaystyle \alpha ^{i_{1}}e_{i_{1}}\pm |\alpha ^{i_{2}}|e_{i_{2}}\pm |\alpha ^{i_{3}}|e_{i_{3}}\pm \ldots }
where
α
i
k
≠
0
{\displaystyle \alpha ^{i_{k}}\neq 0}
The output must comply to the following rules:
don't show null terms, unless the whole combination is null.
e(1) is fine, e(1) + 0*e(3) or e(1) + 0 is wrong.
don't show scalars when they are equal to one or minus one.
e(3) is fine, 1*e(3) is wrong.
don't prefix by a minus sign if it follows a preceding term. Instead you use subtraction.
e(4) - e(5) is fine, e(4) + -e(5) is wrong.
Show here output for the following lists of scalars:
1) 1, 2, 3
2) 0, 1, 2, 3
3) 1, 0, 3, 4
4) 1, 2, 0
5) 0, 0, 0
6) 0
7) 1, 1, 1
8) -1, -1, -1
9) -1, -2, 0, -3
10) -1
| #Java | Java | import java.util.Arrays;
public class LinearCombination {
private static String linearCombo(int[] c) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < c.length; ++i) {
if (c[i] == 0) continue;
String op;
if (c[i] < 0 && sb.length() == 0) {
op = "-";
} else if (c[i] < 0) {
op = " - ";
} else if (c[i] > 0 && sb.length() == 0) {
op = "";
} else {
op = " + ";
}
int av = Math.abs(c[i]);
String coeff = av == 1 ? "" : "" + av + "*";
sb.append(op).append(coeff).append("e(").append(i + 1).append(')');
}
if (sb.length() == 0) {
return "0";
}
return sb.toString();
}
public static void main(String[] args) {
int[][] combos = new int[][]{
new int[]{1, 2, 3},
new int[]{0, 1, 2, 3},
new int[]{1, 0, 3, 4},
new int[]{1, 2, 0},
new int[]{0, 0, 0},
new int[]{0},
new int[]{1, 1, 1},
new int[]{-1, -1, -1},
new int[]{-1, -2, 0, -3},
new int[]{-1},
};
for (int[] c : combos) {
System.out.printf("%-15s -> %s\n", Arrays.toString(c), linearCombo(c));
}
}
} |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Mathematica_.2F_Wolfram_Language | Mathematica / Wolfram Language | f[x_,y_] := x + y (* Function comment : adds two numbers *)
f::usage = "f[x,y] gives the sum of x and y"
?f
-> f[x,y] gives the sum of x and y |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #MATLAB_.2F_Octave | MATLAB / Octave | function Gnash(GnashFile); %Convert to a "function". Data is placed in the "global" area.
% My first MatLab attempt, to swallow data as produced by Gnash's DUMP
%command in a comma-separated format. Such files start with a line |
http://rosettacode.org/wiki/Documentation | Documentation |
See also
Related task: Comments
Related task: Here_document
| #Neko | Neko | /** ... **/ |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #jq | jq | def diversitytheorem($actual; $predicted):
def mean: add/length;
($predicted | mean) as $mean
| { avgerr: ($predicted | map(. - $actual) | map(pow(.; 2)) | mean),
crderr: pow($mean - $actual; 2),
divers: ($predicted | map(. - $mean) | map(pow(.;2)) | mean) } ; |
http://rosettacode.org/wiki/Diversity_prediction_theorem | Diversity prediction theorem | The wisdom of the crowd is the collective opinion of a group of individuals rather than that of a single expert.
Wisdom-of-the-crowds research routinely attributes the superiority of crowd averages over individual judgments to the elimination of individual noise, an explanation that assumes independence of the individual judgments from each other.
Thus the crowd tends to make its best decisions if it is made up of diverse opinions and ideologies.
Scott E. Page introduced the diversity prediction theorem:
The squared error of the collective prediction equals the average squared error minus the predictive diversity.
Therefore, when the diversity in a group is large, the error of the crowd is small.
Definitions
Average Individual Error: Average of the individual squared errors
Collective Error: Squared error of the collective prediction
Prediction Diversity: Average squared distance from the individual predictions to the collective prediction
Diversity Prediction Theorem: Given a crowd of predictive models, then
Collective Error = Average Individual Error ─ Prediction Diversity
Task
For a given true value and a number of number of estimates (from a crowd), show (here on this page):
the true value and the crowd estimates
the average error
the crowd error
the prediction diversity
Use (at least) these two examples:
a true value of 49 with crowd estimates of: 48 47 51
a true value of 49 with crowd estimates of: 48 47 51 42
Also see
Wikipedia entry: Wisdom of the crowd
University of Michigan: PDF paper (exists on a web archive, the Wayback Machine).
| #Julia | Julia | import Statistics: mean
function diversitytheorem(truth::T, pred::Vector{T}) where T<:Number
μ = mean(pred)
avgerr = mean((pred .- truth) .^ 2)
crderr = (μ - truth) ^ 2
divers = mean((pred .- μ) .^ 2)
avgerr, crderr, divers
end
for (t, s) in [(49, [48, 47, 51]),
(49, [48, 47, 51, 42])]
avgerr, crderr, divers = diversitytheorem(t, s)
println("""
average-error : $avgerr
crowd-error : $crderr
diversity : $divers
""")
end |
http://rosettacode.org/wiki/Draw_a_sphere | Draw a sphere | Task
Draw a sphere.
The sphere can be represented graphically, or in ASCII art, depending on the language capabilities.
Either static or rotational projection is acceptable for this task.
Related tasks
draw a cuboid
draw a rotating cube
write language name in 3D ASCII
draw a Deathstar
| #Turing | Turing | % Draw a sphere in ASCII art in Turing
% Light intensity to character map
const shades := '.:!*oe&#%@'
const maxShades := length (shades)
% Absolute dot product of x and y
function dot (x, y : array 1 .. 3 of real) : real
result abs (x(1) * y(1) + x(2) * y(2) + x(3) * y(3))
end dot
% Vector normalization
procedure normalize (var v : array 1 .. 3 of real)
const norm := sqrt (v(1)**2 + v(2)**2 + v(3)**2)
for i : 1 .. 3
v(i) := v(i) / norm
end for
end normalize
% Draws a sphere using ASCII art
procedure drawSphere (radius : real, k : int, lightsource : array 1 .. 3 of real, brightness : real)
const diameter := 2.0 * radius
for i : floor (-radius) .. ceil (radius)
var x := i + 0.5
for j : floor (-diameter) .. ceil (diameter)
var y := j / 2 + 0.5
if x**2 + y**2 <= radius**2 then
var vec : array 1 .. 3 of real
vec(1) := x; vec(2) := y; vec(3) := sqrt (radius**2 - x**2 - y**2)
normalize (vec)
const b := dot (lightsource, vec) ** k + brightness
var intensity := round ((1 - b) * maxShades)
if intensity < 1 then
intensity := 1
elsif intensity > maxShades then
intensity := maxShades
end if
put shades (intensity) ..
else
put ' ' ..
end if
end for
put ""
end for
end drawSphere
% Light source
var lightsource : array 1 .. 3 of real := init (30, 30, -59)
normalize (lightsource)
const brightness := 0.1
% Draw some spheres
drawSphere (20, 4, lightsource, brightness)
drawSphere (15, 10, lightsource, brightness) |
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