task_url stringlengths 30 116 | task_name stringlengths 2 86 | task_description stringlengths 0 14.4k | language_url stringlengths 2 53 | language_name stringlengths 1 52 | code stringlengths 0 61.9k |
|---|---|---|---|---|---|
http://rosettacode.org/wiki/Empty_program | Empty program | Task
Create the simplest possible program that is still considered "correct."
| #ALGOL_W | ALGOL W | . |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #Pascal | Pascal | use constant PI => 3.14159;
use constant MSG => "Hello World"; |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #Perl | Perl | use constant PI => 3.14159;
use constant MSG => "Hello World"; |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #Phix | Phix | with javascript_semantics
constant n = 1
constant s = {1,2,3}
constant str = "immutable string"
|
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #PHP | PHP | define("PI", 3.14159265358);
define("MSG", "Hello World"); |
http://rosettacode.org/wiki/Entropy | Entropy | Task
Calculate the Shannon entropy H of a given input string.
Given the discrete random variable
X
{\displaystyle X}
that is a string of
N
{\displaystyle N}
"symbols" (total characters) consisting of
n
{\displaystyle n}
different characters (n=2 for binary), the Shannon entropy of X in bit... | #Clojure | Clojure | (defn entropy [s]
(let [len (count s), log-2 (Math/log 2)]
(->> (frequencies s)
(map (fn [[_ v]]
(let [rf (/ v len)]
(-> (Math/log rf) (/ log-2) (* rf) Math/abs))))
(reduce +)))) |
http://rosettacode.org/wiki/Ethiopian_multiplication | Ethiopian multiplication | Ethiopian multiplication is a method of multiplying integers using only addition, doubling, and halving.
Method:
Take two numbers to be multiplied and write them down at the top of two columns.
In the left-hand column repeatedly halve the last number, discarding any remainders, and write the result below the last ... | #Clojure | Clojure | (defn halve [n]
(bit-shift-right n 1))
(defn twice [n] ; 'double' is taken
(bit-shift-left n 1))
(defn even [n] ; 'even?' is the standard fn
(zero? (bit-and n 1)))
(defn emult [x y]
(reduce +
(map second
(filter #(not (even (first %))) ; a.k.a. 'odd?'
(take-while #(p... |
http://rosettacode.org/wiki/Equilibrium_index | Equilibrium index | An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.
For example, in a sequence
A
{\displaystyle A}
:
A
0
=
−
7
{\displaystyle A_{0}=-7}
A
1
=
1
{\displaystyle A_{1}=1}
... | #Icon_and_Unicon | Icon and Unicon | procedure main(arglist)
L := if *arglist > 0 then arglist else [-7, 1, 5, 2, -4, 3, 0] # command line args or default
every writes( "equilibrium indicies of [ " | (!L ||" ") | "] = " | (eqindex(L)||" ") | "\n" )
end
procedure eqindex(L) # generate equilibrium points in a list L or fail
local s,l,i
every (s := 0, ... |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #Maple | Maple | getenv("PATH"); |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #Mathematica_.2F_Wolfram_Language | Mathematica / Wolfram Language | Environment["PATH"] |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #MATLAB_.2F_Octave | MATLAB / Octave | getenv('HOME')
getenv('PATH')
getenv('USER') |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #Mercury | Mercury | :- module env_var.
:- interface.
:- import_module io.
:- pred main(io::di, io::uo) is det.
:- implementation.
:- import_module maybe, string.
main(!IO) :-
io.get_environment_var("HOME", MaybeValue, !IO),
(
MaybeValue = yes(Value),
io.write_string("HOME is " ++ Value ++ "\n", !IO)
;
... |
http://rosettacode.org/wiki/Esthetic_numbers | Esthetic numbers | An esthetic number is a positive integer where every adjacent digit differs from its neighbour by 1.
E.G.
12 is an esthetic number. One and two differ by 1.
5654 is an esthetic number. Each digit is exactly 1 away from its neighbour.
890 is not an esthetic number. Nine and zero differ by 9.
These examples are n... | #Sidef | Sidef | func generate_esthetic(root, upto, callback, b=10) {
var v = root.digits2num(b)
return nil if (v > upto)
callback(v)
var t = root.head
__FUNC__([t+1, root...], upto, callback, b) if (t+1 < b)
__FUNC__([t-1, root...], upto, callback, b) if (t-1 >= 0)
}
func between_esthetic(from, upto,... |
http://rosettacode.org/wiki/Euler%27s_sum_of_powers_conjecture | Euler's sum of powers conjecture | There is a conjecture in mathematics that held for over two hundred years before it was disproved by the finding of a counterexample in 1966 by Lander and Parkin.
Euler's (disproved) sum of powers conjecture
At least k positive kth powers are required to sum to a kth power,
except for the trivial case... | #FreeBASIC | FreeBASIC | ' version 14-09-2015
' compile with: fbc -s console
' some constants calculated when the program is compiled
Const As UInteger max = 250
Const As ULongInt pow5_max = CULngInt(max) * max * max * max * max
' limit x1, x2, x3
Const As UInteger limit_x1 = (pow5_max / 4) ^ 0.2
Const As UInteger limit_x2 = (pow5_max / 3)... |
http://rosettacode.org/wiki/Factorial | Factorial | Definitions
The factorial of 0 (zero) is defined as being 1 (unity).
The Factorial Function of a positive integer, n, is defined as the product of the sequence:
n, n-1, n-2, ... 1
Task
Write a function to return the factorial of a number.
Solutions can be iterat... | #Nim | Nim |
import math
let i:int = fac(x)
|
http://rosettacode.org/wiki/Even_or_odd | Even or odd | Task
Test whether an integer is even or odd.
There is more than one way to solve this task:
Use the even and odd predicates, if the language provides them.
Check the least significant digit. With binary integers, i bitwise-and 1 equals 0 iff i is even, or equals 1 iff i is odd.
Divide i by 2. The remainder equals... | #Clojure | Clojure | (if (even? some-var) (do-even-stuff))
(if (odd? some-var) (do-odd-stuff)) |
http://rosettacode.org/wiki/Euler_method | Euler method | Euler's method numerically approximates solutions of first-order ordinary differential equations (ODEs) with a given initial value. It is an explicit method for solving initial value problems (IVPs), as described in the wikipedia page.
The ODE has to be provided in the following form:
d
y
(
t
)
d
t
=
f... | #Ring | Ring |
decimals(3)
see euler("return -0.07*(y-20)", 100, 0, 100, 2) + nl
see euler("return -0.07*(y-20)", 100, 0, 100, 5) + nl
see euler("return -0.07*(y-20)", 100, 0, 100, 10) + nl
func euler df, y, a, b, s
t = a
while t <= b
see "" + t + " " + y + nl
y += s * eval(df)
... |
http://rosettacode.org/wiki/Euler_method | Euler method | Euler's method numerically approximates solutions of first-order ordinary differential equations (ODEs) with a given initial value. It is an explicit method for solving initial value problems (IVPs), as described in the wikipedia page.
The ODE has to be provided in the following form:
d
y
(
t
)
d
t
=
f... | #Ruby | Ruby | def euler(y, a, b, h)
a.step(b,h) do |t|
puts "%7.3f %7.3f" % [t,y]
y += h * yield(t,y)
end
end
[10, 5, 2].each do |step|
puts "Step = #{step}"
euler(100,0,100,step) {|time, temp| -0.07 * (temp - 20) }
puts
end |
http://rosettacode.org/wiki/Evaluate_binomial_coefficients | Evaluate binomial coefficients | This programming task, is to calculate ANY binomial coefficient.
However, it has to be able to output
(
5
3
)
{\displaystyle {\binom {5}{3}}}
, which is 10.
This formula is recommended:
(
n
k
)
=
n
!
(
n
−
k
)
!
k
!
=
n
(
n
−
1
)
(
n
−
2
)
…
(
n
−
k
+
1
)
k
(
k
−
1... | #Julia | Julia | @show binomial(5, 3) |
http://rosettacode.org/wiki/Evaluate_binomial_coefficients | Evaluate binomial coefficients | This programming task, is to calculate ANY binomial coefficient.
However, it has to be able to output
(
5
3
)
{\displaystyle {\binom {5}{3}}}
, which is 10.
This formula is recommended:
(
n
k
)
=
n
!
(
n
−
k
)
!
k
!
=
n
(
n
−
1
)
(
n
−
2
)
…
(
n
−
k
+
1
)
k
(
k
−
1... | #K | K | {[n;k]_(*/(k-1)_1+!n)%(*/1+!k)} . 5 3
10 |
http://rosettacode.org/wiki/Emirp_primes | Emirp primes | An emirp (prime spelled backwards) are primes that when reversed (in their decimal representation) are a different prime.
(This rules out palindromic primes.)
Task
show the first twenty emirps
show all emirps between 7,700 and 8,000
show the 10,000th emirp
In each list, the numbe... | #AWK | AWK |
function is_prime(n, p)
{
if (!(n%2) || !(n%3)) {
return 0 }
p = 1
while(p*p < n)
if (n%(p += 4) == 0 || n%(p += 2) == 0) {
return 0 }
return 1
}
function reverse(n, r)
{
r = 0
for (r = 0; int(n) != 0; n /= 10)
r = r*... |
http://rosettacode.org/wiki/Elliptic_curve_arithmetic | Elliptic curve arithmetic | Elliptic curves are sometimes used in cryptography as a way to perform digital signatures.
The purpose of this task is to implement a simplified (without modular arithmetic) version of the elliptic curve arithmetic which is required by the elliptic curve DSA protocol.
In a nutshell, an elliptic curve is a... | #Java | Java | import static java.lang.Math.*;
import java.util.Locale;
public class Test {
public static void main(String[] args) {
Pt a = Pt.fromY(1);
Pt b = Pt.fromY(2);
System.out.printf("a = %s%n", a);
System.out.printf("b = %s%n", b);
Pt c = a.plus(b);
System.out.printf("c... |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #JSON | JSON | {"fruits" : { "apple" : null, "banana" : null, "cherry" : null }
{"fruits" : { "apple" : 0, "banana" : 1, "cherry" : 2 } |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #Julia | Julia |
@enum Fruits APPLE BANANA CHERRY
|
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #Kotlin | Kotlin | // version 1.0.5-2
enum class Animals {
CAT, DOG, ZEBRA
}
enum class Dogs(val id: Int) {
BULLDOG(1), TERRIER(2), WOLFHOUND(4)
}
fun main(args: Array<String>) {
for (value in Animals.values()) println("${value.name.padEnd(5)} : ${value.ordinal}")
println()
for (value in Dogs.values()) println("... |
http://rosettacode.org/wiki/Elementary_cellular_automaton/Random_Number_Generator | Elementary cellular automaton/Random Number Generator | Rule 30 is considered to be chaotic enough to generate good pseudo-random numbers. As a matter of fact, rule 30 is used by the Mathematica software for its default random number generator.
Steven Wolfram's recommendation for random number generation from rule 30 consists in extracting successive bits in a fixed positi... | #Perl | Perl | package Automaton {
sub new {
my $class = shift;
my $rule = [ reverse split //, sprintf "%08b", shift ];
return bless { rule => $rule, cells => [ @_ ] }, $class;
}
sub next {
my $this = shift;
my @previous = @{$this->{cells}};
$this->{cells} = [
@{$this->{rule}}[
map ... |
http://rosettacode.org/wiki/Empty_string | Empty string | Languages may have features for dealing specifically with empty strings
(those containing no characters).
Task
Demonstrate how to assign an empty string to a variable.
Demonstrate how to check that a string is empty.
Demonstrate how to check that a string is not empty.
Other tasks related to string oper... | #Arturo | Arturo | s: ""
if empty? s -> print "the string is empty"
if 0 = size s -> print "yes, the string is empty"
s: "hello world"
if not? empty? s -> print "the string is not empty"
if 0 < size s -> print "no, the string is not empty" |
http://rosettacode.org/wiki/Empty_string | Empty string | Languages may have features for dealing specifically with empty strings
(those containing no characters).
Task
Demonstrate how to assign an empty string to a variable.
Demonstrate how to check that a string is empty.
Demonstrate how to check that a string is not empty.
Other tasks related to string oper... | #Asymptote | Asymptote | string c; //implicitly assigned an empty string
if (length(c) == 0) {
write("Empty string");
} else {
write("Non empty string");
}
string s = ""; //explicitly assigned an empty string
if (s == "") {
write("Empty string");
}
if (s != "") {
write("Non empty string");
}
string t = "not empty";
if (t != "")... |
http://rosettacode.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm | Elliptic Curve Digital Signature Algorithm | Elliptic curves.
An elliptic curve E over ℤp (p ≥ 5) is defined by an equation of the form
y^2 = x^3 + ax + b, where a, b ∈ ℤp and the discriminant ≢ 0 (mod p),
together with a special point 𝒪 called the point at infinity.
The set E(ℤp) consists of all points (x, y), with x, y ∈ ℤp,
which satisfy the above defining eq... | #Wren | Wren | import "/dynamic" for Struct
import "/big" for BigInt
import "/fmt" for Fmt
import "/math" for Boolean
import "random" for Random
var rand = Random.new()
// rational ec point: x and y are BigInts
var Epnt = Struct.create("Epnt", ["x", "y"])
// elliptic curve parameters: N is a BigInt, G is an Epnt, rest are integ... |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #Elixir | Elixir | path = hd(System.argv)
IO.puts File.dir?(path) and Enum.empty?( File.ls!(path) ) |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #Erlang | Erlang | 3> {ok, []} = file:list_dir_all("/usr").
** exception error: no match of right hand side value
{ok,["X11R6","X11","standalone","share","sbin","local",
"libexec","lib","bin"]}
4> {ok, []} = file:list_dir_all("/asd").
** exception error: no match of right hand side value {... |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #F.23 | F# | open System.IO
let isEmptyDirectory x = (Directory.GetFiles x).Length = 0 && (Directory.GetDirectories x).Length = 0 |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #Factor | Factor | USE: io.directories
: empty-directory? ( path -- ? ) directory-entries empty? ; |
http://rosettacode.org/wiki/Empty_program | Empty program | Task
Create the simplest possible program that is still considered "correct."
| #AmigaE | AmigaE | PROC main()
ENDPROC |
http://rosettacode.org/wiki/Empty_program | Empty program | Task
Create the simplest possible program that is still considered "correct."
| #AppleScript | AppleScript | return |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #PicoLisp | PicoLisp | : (de pi () 4)
-> pi
: (pi)
-> 4 |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #PL.2FI | PL/I | *process source attributes xref;
constants: Proc Options(main);
Dcl three Bin Fixed(15) Value(3);
Put Skip List(1/three);
Put Skip List(1/3);
End; |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #PowerBASIC | PowerBASIC | $me = "myname"
%age = 35 |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #PureBasic | PureBasic | #i_Const1 = 11
#i_Const2 = 3.1415
#i_Const3 = "A'm a string" |
http://rosettacode.org/wiki/Entropy | Entropy | Task
Calculate the Shannon entropy H of a given input string.
Given the discrete random variable
X
{\displaystyle X}
that is a string of
N
{\displaystyle N}
"symbols" (total characters) consisting of
n
{\displaystyle n}
different characters (n=2 for binary), the Shannon entropy of X in bit... | #CLU | CLU | % NOTE: when compiling with Portable CLU,
% this program needs to be merged with 'useful.lib' to get log()
%
% pclu -merge $CLUHOME/lib/useful.lib -compile entropy.clu
shannon = proc (s: string) returns (real)
% find the frequency of each character
freq: array[int] := array[int]$fill(0, 256, 0)
for c: cha... |
http://rosettacode.org/wiki/Entropy | Entropy | Task
Calculate the Shannon entropy H of a given input string.
Given the discrete random variable
X
{\displaystyle X}
that is a string of
N
{\displaystyle N}
"symbols" (total characters) consisting of
n
{\displaystyle n}
different characters (n=2 for binary), the Shannon entropy of X in bit... | #CoffeeScript | CoffeeScript | entropy = (s) ->
freq = (s) ->
result = {}
for ch in s.split ""
result[ch] ?= 0
result[ch]++
return result
frq = freq s
n = s.length
((frq[f]/n for f of frq).reduce ((e, p) -> e - p * Math.log(p)), 0) * Math.LOG2E
console.log "The entropy of the string... |
http://rosettacode.org/wiki/Ethiopian_multiplication | Ethiopian multiplication | Ethiopian multiplication is a method of multiplying integers using only addition, doubling, and halving.
Method:
Take two numbers to be multiplied and write them down at the top of two columns.
In the left-hand column repeatedly halve the last number, discarding any remainders, and write the result below the last ... | #CLU | CLU | halve = proc (n: int) returns (int)
return(n/2)
end halve
double = proc (n: int) returns (int)
return(n*2)
end double
even = proc (n: int) returns (bool)
return(n//2 = 0)
end even
e_mul = proc (a, b: int) returns (int)
total: int := 0
while (a > 0) do
if ~even(a) then total := total ... |
http://rosettacode.org/wiki/Equilibrium_index | Equilibrium index | An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.
For example, in a sequence
A
{\displaystyle A}
:
A
0
=
−
7
{\displaystyle A_{0}=-7}
A
1
=
1
{\displaystyle A_{1}=1}
... | #J | J | equilidx=: +/\ I.@:= +/\. |
http://rosettacode.org/wiki/Equilibrium_index | Equilibrium index | An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.
For example, in a sequence
A
{\displaystyle A}
:
A
0
=
−
7
{\displaystyle A_{0}=-7}
A
1
=
1
{\displaystyle A_{1}=1}
... | #Java | Java |
public class Equlibrium {
public static void main(String[] args) {
int[] sequence = {-7, 1, 5, 2, -4, 3, 0};
equlibrium_indices(sequence);
}
public static void equlibrium_indices(int[] sequence){
//find total sum
int totalSum = 0;
for (int n : sequence) {
totalSum += n;
}
//compare running sum t... |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #min | min | $PATH |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #Modula-3 | Modula-3 | MODULE EnvVars EXPORTS Main;
IMPORT IO, Env;
VAR
k, v: TEXT;
BEGIN
IO.Put(Env.Get("HOME") & "\n");
FOR i := 0 TO Env.Count - 1 DO
Env.GetNth(i, k, v);
IO.Put(k & " = " & v & "\n")
END
END EnvVars. |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #MUMPS | MUMPS | Set X=$ZF(-1,"show logical")
Set X=$ZF(-1,"show symbol") |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #NetRexx | NetRexx | /* NetRexx */
options replace format comments java crossref symbols nobinary
runSample(arg)
return
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method sysEnvironment(vn = '') public static
if vn.length > 0 then do
envName = vn
envValu = System.getenv(envName)
if env... |
http://rosettacode.org/wiki/Esthetic_numbers | Esthetic numbers | An esthetic number is a positive integer where every adjacent digit differs from its neighbour by 1.
E.G.
12 is an esthetic number. One and two differ by 1.
5654 is an esthetic number. Each digit is exactly 1 away from its neighbour.
890 is not an esthetic number. Nine and zero differ by 9.
These examples are n... | #Swift | Swift | extension Sequence {
func take(_ n: Int) -> [Element] {
var res = [Element]()
for el in self {
guard res.count != n else {
return res
}
res.append(el)
}
return res
}
}
extension String {
func isEsthetic(base: Int = 10) -> Bool {
zip(dropFirst(0), dropFirst())
... |
http://rosettacode.org/wiki/Euler%27s_sum_of_powers_conjecture | Euler's sum of powers conjecture | There is a conjecture in mathematics that held for over two hundred years before it was disproved by the finding of a counterexample in 1966 by Lander and Parkin.
Euler's (disproved) sum of powers conjecture
At least k positive kth powers are required to sum to a kth power,
except for the trivial case... | #Go | Go | package main
import (
"fmt"
"log"
)
func main() {
fmt.Println(eulerSum())
}
func eulerSum() (x0, x1, x2, x3, y int) {
var pow5 [250]int
for i := range pow5 {
pow5[i] = i * i * i * i * i
}
for x0 = 4; x0 < len(pow5); x0++ {
for x1 = 3; x1 < x0; x1++ {
for x2 = 2; x2 < x1; x2++ {
for x3 = 1; x3 < ... |
http://rosettacode.org/wiki/Factorial | Factorial | Definitions
The factorial of 0 (zero) is defined as being 1 (unity).
The Factorial Function of a positive integer, n, is defined as the product of the sequence:
n, n-1, n-2, ... 1
Task
Write a function to return the factorial of a number.
Solutions can be iterat... | #Niue | Niue | [ dup 1 > [ dup 1 - factorial * ] when ] 'factorial ;
( test )
4 factorial . ( => 24 )
10 factorial . ( => 3628800 ) |
http://rosettacode.org/wiki/Even_or_odd | Even or odd | Task
Test whether an integer is even or odd.
There is more than one way to solve this task:
Use the even and odd predicates, if the language provides them.
Check the least significant digit. With binary integers, i bitwise-and 1 equals 0 iff i is even, or equals 1 iff i is odd.
Divide i by 2. The remainder equals... | #COBOL | COBOL | IF FUNCTION REM(Num, 2) = 0
DISPLAY Num " is even."
ELSE
DISPLAY Num " is odd."
END-IF |
http://rosettacode.org/wiki/Even_or_odd | Even or odd | Task
Test whether an integer is even or odd.
There is more than one way to solve this task:
Use the even and odd predicates, if the language provides them.
Check the least significant digit. With binary integers, i bitwise-and 1 equals 0 iff i is even, or equals 1 iff i is odd.
Divide i by 2. The remainder equals... | #CoffeeScript | CoffeeScript | isEven = (x) -> !(x%2) |
http://rosettacode.org/wiki/Euler_method | Euler method | Euler's method numerically approximates solutions of first-order ordinary differential equations (ODEs) with a given initial value. It is an explicit method for solving initial value problems (IVPs), as described in the wikipedia page.
The ODE has to be provided in the following form:
d
y
(
t
)
d
t
=
f... | #Rust | Rust | fn header() {
print!(" Time: ");
for t in (0..100).step_by(10) {
print!(" {:7}", t);
}
println!();
}
fn analytic() {
print!("Analytic: ");
for t in (0..=100).step_by(10) {
print!(" {:7.3}", 20.0 + 80.0 * (-0.07 * f64::from(t)).exp());
}
println!();
}
fn euler<F: Fn... |
http://rosettacode.org/wiki/Euler_method | Euler method | Euler's method numerically approximates solutions of first-order ordinary differential equations (ODEs) with a given initial value. It is an explicit method for solving initial value problems (IVPs), as described in the wikipedia page.
The ODE has to be provided in the following form:
d
y
(
t
)
d
t
=
f... | #Scala | Scala |
object App{
def main(args : Array[String]) = {
def cooling( step : Int ) = {
eulerStep( (step , y) => {-0.07 * (y - 20)} ,
100.0,0,100,step)
}
cooling(10)
cooling(5)
cooling(2)
}
def eulerStep( func : (Int,Double) => Double,y0 : Double,
begin : Int, end : Int , step : ... |
http://rosettacode.org/wiki/Evaluate_binomial_coefficients | Evaluate binomial coefficients | This programming task, is to calculate ANY binomial coefficient.
However, it has to be able to output
(
5
3
)
{\displaystyle {\binom {5}{3}}}
, which is 10.
This formula is recommended:
(
n
k
)
=
n
!
(
n
−
k
)
!
k
!
=
n
(
n
−
1
)
(
n
−
2
)
…
(
n
−
k
+
1
)
k
(
k
−
1... | #Kotlin | Kotlin | // version 2.0
fun binomial(n: Int, k: Int) = when {
n < 0 || k < 0 -> throw IllegalArgumentException("negative numbers not allowed")
n == k -> 1L
else -> {
val kReduced = min(k, n - k) // minimize number of steps
var result = 1L
var numerator = n
var d... |
http://rosettacode.org/wiki/Emirp_primes | Emirp primes | An emirp (prime spelled backwards) are primes that when reversed (in their decimal representation) are a different prime.
(This rules out palindromic primes.)
Task
show the first twenty emirps
show all emirps between 7,700 and 8,000
show the 10,000th emirp
In each list, the numbe... | #C | C | #include <stdio.h>
typedef unsigned uint;
int is_prime(uint n)
{
if (!(n%2) || !(n%3)) return 0;
uint p = 1;
while(p*p < n)
if (n%(p += 4) == 0 || n%(p += 2) == 0)
return 0;
return 1;
}
uint reverse(uint n)
{
uint r;
for (r = 0;... |
http://rosettacode.org/wiki/Elliptic_curve_arithmetic | Elliptic curve arithmetic | Elliptic curves are sometimes used in cryptography as a way to perform digital signatures.
The purpose of this task is to implement a simplified (without modular arithmetic) version of the elliptic curve arithmetic which is required by the elliptic curve DSA protocol.
In a nutshell, an elliptic curve is a... | #Julia | Julia | struct Point{T<:AbstractFloat}
x::T
y::T
end
Point{T}() where T<:AbstractFloat = Point{T}(Inf, Inf)
Point() = Point{Float64}()
Base.show(io::IO, p::Point{T}) where T = iszero(p) ? print(io, "Zero{$T}") : @printf(io, "{%s}(%.3f, %.3f)", T, p.x, p.y)
Base.copy(p::Point) = Point(p.x, p.y)
Base.iszero(p::Point{T}... |
http://rosettacode.org/wiki/Elliptic_curve_arithmetic | Elliptic curve arithmetic | Elliptic curves are sometimes used in cryptography as a way to perform digital signatures.
The purpose of this task is to implement a simplified (without modular arithmetic) version of the elliptic curve arithmetic which is required by the elliptic curve DSA protocol.
In a nutshell, an elliptic curve is a... | #Kotlin | Kotlin | // version 1.1.4
const val C = 7
class Pt(val x: Double, val y: Double) {
val zero get() = Pt(Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY)
val isZero get() = x > 1e20 || x < -1e20
fun dbl(): Pt {
if (isZero) return this
val l = 3.0 * x * x / (2.0 * y)
val t = l * l - 2... |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #Lingo | Lingo | -- parent script "Enumeration"
property ancestor
on new (me)
data = [:]
repeat with i = 2 to the paramCount
data[param(i)] = i-1
end repeat
me.ancestor = data
return me
end
on setAt (me)
-- do nothing
end
on setProp (me)
-- do nothing
end
on deleteAt (me)
-- do nothing
end
on deleteProp ... |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #Lua | Lua |
local fruit = {apple = 0, banana = 1, cherry = 2}
|
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #M2000_Interpreter | M2000 Interpreter |
Module Checkit {
\\ need revision 15, version 9.4
Enum Fruit {apple, banana, cherry}
Enum Fruit2 {apple2=10, banana2=20, cherry2=30}
Print apple, banana, cherry
Print apple2, banana2, cherry2
Print Len(apple)=0
Print Len(banana)=1
Print Len(cherry)=2
Print Len(c... |
http://rosettacode.org/wiki/Elementary_cellular_automaton/Random_Number_Generator | Elementary cellular automaton/Random Number Generator | Rule 30 is considered to be chaotic enough to generate good pseudo-random numbers. As a matter of fact, rule 30 is used by the Mathematica software for its default random number generator.
Steven Wolfram's recommendation for random number generation from rule 30 consists in extracting successive bits in a fixed positi... | #Phix | Phix | with javascript_semantics
--string s = ".........#.........", --(original)
string s = "...............................#"&
"................................",
--string s = "#"&repeat('.',100), -- [2]
t=s, r = "........"
integer rule = 30, k, l = length(s), w = 0
for i=1 to 8 do
r[i] = iff(mod(ru... |
http://rosettacode.org/wiki/Elementary_cellular_automaton/Random_Number_Generator | Elementary cellular automaton/Random Number Generator | Rule 30 is considered to be chaotic enough to generate good pseudo-random numbers. As a matter of fact, rule 30 is used by the Mathematica software for its default random number generator.
Steven Wolfram's recommendation for random number generation from rule 30 consists in extracting successive bits in a fixed positi... | #Python | Python | from elementary_cellular_automaton import eca, eca_wrap
def rule30bytes(lencells=100):
cells = '1' + '0' * (lencells - 1)
gen = eca(cells, 30)
while True:
yield int(''.join(next(gen)[0] for i in range(8)), 2)
if __name__ == '__main__':
print([b for i,b in zip(range(10), rule30bytes())]) |
http://rosettacode.org/wiki/Empty_string | Empty string | Languages may have features for dealing specifically with empty strings
(those containing no characters).
Task
Demonstrate how to assign an empty string to a variable.
Demonstrate how to check that a string is empty.
Demonstrate how to check that a string is not empty.
Other tasks related to string oper... | #AutoHotkey | AutoHotkey | ;; Traditional
; Assign an empty string:
var =
; Check that a string is empty:
If var =
MsgBox the var is empty
; Check that a string is not empty
If var !=
Msgbox the var is not empty
;; Expression mode:
; Assign an empty string:
var := ""
; Check that a string is empty:
If (var = "")
MsgBox the var is em... |
http://rosettacode.org/wiki/Empty_string | Empty string | Languages may have features for dealing specifically with empty strings
(those containing no characters).
Task
Demonstrate how to assign an empty string to a variable.
Demonstrate how to check that a string is empty.
Demonstrate how to check that a string is not empty.
Other tasks related to string oper... | #Avail | Avail | emptyStringVar : string := "";
Assert: emptyStringVar = "";
Assert: emptyStringVar = <>;
Assert: emptyStringVar is empty;
Assert: |emptyStringVar| = 0; |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #FreeBASIC | FreeBASIC | ' FB 1.05.0 Win64
#Include "dir.bi"
Function IsDirEmpty(dirPath As String) As Boolean
Err = 0
' check dirPath is a valid directory
Dim As String fileName = Dir(dirPath, fbDirectory)
If Len(fileName) = 0 Then
Err = 1000 ' dirPath is not a valid path
Return False
End If
' now check if there are a... |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #Gambas | Gambas | Public Sub Main()
Dim sFolder As String = User.home &/ "Rosetta"
Dim sDir As String[] = Dir(sFolder)
Dim sTemp As String
Dim sOutput As String = sfolder & " is NOT empty"
Try sTemp = sDir[0]
If Error Then sOutput = sfolder & " is empty"
Print sOutput
End |
http://rosettacode.org/wiki/Empty_program | Empty program | Task
Create the simplest possible program that is still considered "correct."
| #Argile | Argile | |
http://rosettacode.org/wiki/Empty_program | Empty program | Task
Create the simplest possible program that is still considered "correct."
| #ARM_Assembly | ARM Assembly | .text
.global _start
_start:
mov r0, #0
mov r7, #1
svc #0 |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #Python | Python | >>> s = "Hello"
>>> s[0] = "h"
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
s[0] = "h"
TypeError: 'str' object does not support item assignment |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #Racket | Racket | (struct coordinate (x y)) ; immutable struct |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #Raku | Raku | constant $pi = 3.14159;
constant $msg = "Hello World";
constant @arr = (1, 2, 3, 4, 5); |
http://rosettacode.org/wiki/Enforced_immutability | Enforced immutability | Task
Demonstrate any means your language has to prevent the modification of values, or to create objects that cannot be modified after they have been created.
| #REXX | REXX | /*REXX program emulates immutable variables (as a post-computational check). */
call immutable '$=1' /* ◄─── assigns an immutable variable. */
call immutable ' pi = 3.14159' /* ◄─── " " " " */
call immutable 'radius= 2*pi/4 ' ... |
http://rosettacode.org/wiki/Entropy | Entropy | Task
Calculate the Shannon entropy H of a given input string.
Given the discrete random variable
X
{\displaystyle X}
that is a string of
N
{\displaystyle N}
"symbols" (total characters) consisting of
n
{\displaystyle n}
different characters (n=2 for binary), the Shannon entropy of X in bit... | #Common_Lisp | Common Lisp | (defun entropy (string)
(let ((table (make-hash-table :test 'equal))
(entropy 0))
(mapc (lambda (c) (setf (gethash c table) (+ (gethash c table 0) 1)))
(coerce string 'list))
(maphash (lambda (k v)
(decf entropy (* (/ v (length input-string))
(l... |
http://rosettacode.org/wiki/Ethiopian_multiplication | Ethiopian multiplication | Ethiopian multiplication is a method of multiplying integers using only addition, doubling, and halving.
Method:
Take two numbers to be multiplied and write them down at the top of two columns.
In the left-hand column repeatedly halve the last number, discarding any remainders, and write the result below the last ... | #COBOL | COBOL | *>* Ethiopian multiplication
IDENTIFICATION DIVISION.
PROGRAM-ID. ethiopian-multiplication.
DATA DIVISION.
LOCAL-STORAGE SECTION.
01 l PICTURE 9(10) VALUE 17.
01 r PICTURE 9(10) VALUE 34.
01 ethiopian-multiply PICTURE 9(20).
... |
http://rosettacode.org/wiki/Equilibrium_index | Equilibrium index | An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.
For example, in a sequence
A
{\displaystyle A}
:
A
0
=
−
7
{\displaystyle A_{0}=-7}
A
1
=
1
{\displaystyle A_{1}=1}
... | #JavaScript | JavaScript | function equilibrium(a) {
var N = a.length, i, l = [], r = [], e = []
for (l[0] = a[0], r[N - 1] = a[N - 1], i = 1; i<N; i++)
l[i] = l[i - 1] + a[i], r[N - i - 1] = r[N - i] + a[N - i - 1]
for (i = 0; i < N; i++)
if (l[i] === r[i]) e.push(i)
return e
}
// test & output
[ [-7, 1, 5, 2, -4, 3, 0], // 3,... |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #NewLISP | NewLISP | > (env "SHELL")
"/bin/zsh"
> (env "TERM")
"xterm" |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #Nim | Nim | import os
echo getEnv("HOME") |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #NSIS | NSIS | ExpandEnvStrings $0 "%PATH%" ; Retrieve PATH and place it in builtin register 0.
ExpandEnvStrings $1 "%USERPROFILE%" ; Retrieve the user's profile location and place it in builtin register 1.
ExpandEnvStrings $2 "%USERNAME%" ; Retrieve the user's account name and place it in builtin register 2. |
http://rosettacode.org/wiki/Environment_variables | Environment variables | Task
Show how to get one of your process's environment variables.
The available variables vary by system; some of the common ones available on Unix include:
PATH
HOME
USER
| #Objective-C | Objective-C | [[[NSProcessInfo processInfo] environment] objectForKey:@"HOME"] |
http://rosettacode.org/wiki/Esthetic_numbers | Esthetic numbers | An esthetic number is a positive integer where every adjacent digit differs from its neighbour by 1.
E.G.
12 is an esthetic number. One and two differ by 1.
5654 is an esthetic number. Each digit is exactly 1 away from its neighbour.
890 is not an esthetic number. Nine and zero differ by 9.
These examples are n... | #Wren | Wren | import "./fmt" for Conv, Fmt
var isEsthetic = Fn.new { |n, b|
if (n == 0) return false
var i = n % b
n = (n/b).floor
while (n > 0) {
var j = n % b
if ((i - j).abs != 1) return false
n = (n/b).floor
i = j
}
return true
}
var esths = []
var dfs // recursive f... |
http://rosettacode.org/wiki/Euler%27s_sum_of_powers_conjecture | Euler's sum of powers conjecture | There is a conjecture in mathematics that held for over two hundred years before it was disproved by the finding of a counterexample in 1966 by Lander and Parkin.
Euler's (disproved) sum of powers conjecture
At least k positive kth powers are required to sum to a kth power,
except for the trivial case... | #Groovy | Groovy | class EulerSumOfPowers {
static final int MAX_NUMBER = 250
static void main(String[] args) {
boolean found = false
long[] fifth = new long[MAX_NUMBER]
for (int i = 1; i <= MAX_NUMBER; i++) {
long i2 = i * i
fifth[i - 1] = i2 * i2 * i
}
for (i... |
http://rosettacode.org/wiki/Factorial | Factorial | Definitions
The factorial of 0 (zero) is defined as being 1 (unity).
The Factorial Function of a positive integer, n, is defined as the product of the sequence:
n, n-1, n-2, ... 1
Task
Write a function to return the factorial of a number.
Solutions can be iterat... | #Nyquist | Nyquist | (defun factorial (n)
(do ((x n (* x n)))
((= n 1) x)
(setq n (1- n)))) |
http://rosettacode.org/wiki/Even_or_odd | Even or odd | Task
Test whether an integer is even or odd.
There is more than one way to solve this task:
Use the even and odd predicates, if the language provides them.
Check the least significant digit. With binary integers, i bitwise-and 1 equals 0 iff i is even, or equals 1 iff i is odd.
Divide i by 2. The remainder equals... | #ColdFusion | ColdFusion |
function f(numeric n) {
return n mod 2?"odd":"even"
}
|
http://rosettacode.org/wiki/Even_or_odd | Even or odd | Task
Test whether an integer is even or odd.
There is more than one way to solve this task:
Use the even and odd predicates, if the language provides them.
Check the least significant digit. With binary integers, i bitwise-and 1 equals 0 iff i is even, or equals 1 iff i is odd.
Divide i by 2. The remainder equals... | #Common_Lisp | Common Lisp | (if (evenp some-var) (do-even-stuff))
(if (oddp some-other-var) (do-odd-stuff)) |
http://rosettacode.org/wiki/Euler_method | Euler method | Euler's method numerically approximates solutions of first-order ordinary differential equations (ODEs) with a given initial value. It is an explicit method for solving initial value problems (IVPs), as described in the wikipedia page.
The ODE has to be provided in the following form:
d
y
(
t
)
d
t
=
f... | #SequenceL | SequenceL | import <Utilities/Conversion.sl>;
import <Utilities/Sequence.sl>;
T0 := 100.0;
TR := 20.0;
k := 0.07;
main(args(2)) :=
let
results[i] := euler(newtonCooling, T0, 100, stringToInt(args[i]), 0, "delta_t = " ++ args[i]);
in
delimit(results, '\n');
newtonCooling(t) := -k * (t - TR);
euler: (float -> float) * ... |
http://rosettacode.org/wiki/Euler_method | Euler method | Euler's method numerically approximates solutions of first-order ordinary differential equations (ODEs) with a given initial value. It is an explicit method for solving initial value problems (IVPs), as described in the wikipedia page.
The ODE has to be provided in the following form:
d
y
(
t
)
d
t
=
f... | #Sidef | Sidef | func euler_method(t0, t1, k, step_size) {
var results = [[0, t0]]
for s in (step_size..100 -> by(step_size)) {
t0 -= ((t0 - t1) * k * step_size)
results << [s, t0]
}
return results;
}
func analytical(t0, t1, k, time) {
(t0 - t1) * exp(-time * k) + t1
}
var (T0, T1, k) = (100, 20,... |
http://rosettacode.org/wiki/Evaluate_binomial_coefficients | Evaluate binomial coefficients | This programming task, is to calculate ANY binomial coefficient.
However, it has to be able to output
(
5
3
)
{\displaystyle {\binom {5}{3}}}
, which is 10.
This formula is recommended:
(
n
k
)
=
n
!
(
n
−
k
)
!
k
!
=
n
(
n
−
1
)
(
n
−
2
)
…
(
n
−
k
+
1
)
k
(
k
−
1... | #Lambdatalk | Lambdatalk |
{def C
{lambda {:n :p}
{/ {* {S.serie :n {- :n :p -1} -1}}
{* {S.serie :p 1 -1}}}}}
-> C
{C 16 8}
-> 12870
1{S.map {lambda {:n} {br}1
{S.map {C :n} {S.serie 1 {- :n 1}}} 1}
{S.serie 2 16}}
->
1
1 2 1
1 3 3 1
1 4 6 4 1
1 5 10 10 5 1
1 6 15 20 15 6 1
1 7 21 35 35 21 7 1
1 8 28 56 70 56 28... |
http://rosettacode.org/wiki/Emirp_primes | Emirp primes | An emirp (prime spelled backwards) are primes that when reversed (in their decimal representation) are a different prime.
(This rules out palindromic primes.)
Task
show the first twenty emirps
show all emirps between 7,700 and 8,000
show the 10,000th emirp
In each list, the numbe... | #C.23 | C# | using static System.Console;
using System;
using System.Linq;
using System.Collections.Generic;
public class Program
{
public static void Main() {
const int limit = 1_000_000;
WriteLine("First 20:");
WriteLine(FindEmirpPrimes(limit).Take(20).Delimit());
WriteLine();
Write... |
http://rosettacode.org/wiki/Elliptic_curve_arithmetic | Elliptic curve arithmetic | Elliptic curves are sometimes used in cryptography as a way to perform digital signatures.
The purpose of this task is to implement a simplified (without modular arithmetic) version of the elliptic curve arithmetic which is required by the elliptic curve DSA protocol.
In a nutshell, an elliptic curve is a... | #Nim | Nim | import math, strformat
const B = 7
type Point = tuple[x, y: float]
#---------------------------------------------------------------------------------------------------
template zero(): Point =
(Inf, Inf)
#---------------------------------------------------------------------------------------------------
f... |
http://rosettacode.org/wiki/Elliptic_curve_arithmetic | Elliptic curve arithmetic | Elliptic curves are sometimes used in cryptography as a way to perform digital signatures.
The purpose of this task is to implement a simplified (without modular arithmetic) version of the elliptic curve arithmetic which is required by the elliptic curve DSA protocol.
In a nutshell, an elliptic curve is a... | #OCaml | OCaml |
(* Task : Elliptic_curve_arithmetic *)
(*
Using the secp256k1 elliptic curve (a=0, b=7),
define the addition operation on points on the curve.
Extra credit: define the full elliptic curve arithmetic
(still not modular, though) by defining a "multiply" function.
*)
(*** Helpers ***)
type ec_... |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #M4 | M4 | define(`enums',
`define(`$2',$1)`'ifelse(eval($#>2),1,`enums(incr($1),shift(shift($@)))')')
define(`enum',
`enums(1,$@)')
enum(a,b,c,d)
`c='c |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #Mathematica.2FWolfram_Language | Mathematica/Wolfram Language | MapIndexed[Set, {A, B, F, G}]
->{{1}, {2}, {3}, {4}}
A
->{1}
B
->{2}
G
->{4} |
http://rosettacode.org/wiki/Enumerations | Enumerations | Task
Create an enumeration of constants with and without explicit values.
| #MATLAB_.2F_Octave | MATLAB / Octave | stuff = {'apple', [1 2 3], 'cherry',1+2i}
stuff =
'apple' [1x3 double] 'cherry' [1.000000000000000 + 2.000000000000000i] |
http://rosettacode.org/wiki/Elementary_cellular_automaton/Random_Number_Generator | Elementary cellular automaton/Random Number Generator | Rule 30 is considered to be chaotic enough to generate good pseudo-random numbers. As a matter of fact, rule 30 is used by the Mathematica software for its default random number generator.
Steven Wolfram's recommendation for random number generation from rule 30 consists in extracting successive bits in a fixed positi... | #Racket | Racket | #lang racket
;; below is the code from the parent task
(require "Elementary_cellular_automata.rkt")
(require racket/fixnum)
;; This is the RNG automaton
(define (CA30-random-generator
#:rule [rule 30] ; rule 30 is random, maybe you're interested in using others
;; width of the CA... this is implemen... |
http://rosettacode.org/wiki/Elementary_cellular_automaton/Random_Number_Generator | Elementary cellular automaton/Random Number Generator | Rule 30 is considered to be chaotic enough to generate good pseudo-random numbers. As a matter of fact, rule 30 is used by the Mathematica software for its default random number generator.
Steven Wolfram's recommendation for random number generation from rule 30 consists in extracting successive bits in a fixed positi... | #Raku | Raku | class Automaton {
has $.rule;
has @.cells;
has @.code = $!rule.fmt('%08b').flip.comb».Int;
method gist { "|{ @!cells.map({+$_ ?? '#' !! ' '}).join }|" }
method succ {
self.new: :$!rule, :@!code, :cells(
@!code[
4 «*« @!cells.rotate(-1)
»+«... |
http://rosettacode.org/wiki/Empty_string | Empty string | Languages may have features for dealing specifically with empty strings
(those containing no characters).
Task
Demonstrate how to assign an empty string to a variable.
Demonstrate how to check that a string is empty.
Demonstrate how to check that a string is not empty.
Other tasks related to string oper... | #AWK | AWK | #!/usr/bin/awk -f
BEGIN {
# Demonstrate how to assign an empty string to a variable.
a="";
b="XYZ";
print "a = ",a;
print "b = ",b;
print "length(a)=",length(a);
print "length(b)=",length(b);
# Demonstrate how to check that a string is empty.
print "Is a empty ?",length(a)==0;
print "Is a not ... |
http://rosettacode.org/wiki/Empty_string | Empty string | Languages may have features for dealing specifically with empty strings
(those containing no characters).
Task
Demonstrate how to assign an empty string to a variable.
Demonstrate how to check that a string is empty.
Demonstrate how to check that a string is not empty.
Other tasks related to string oper... | #Axe | Axe | ""→Str1
!If length(Str1)
Disp "EMPTY",i
Else
Disp "NOT EMPTY",i
End |
http://rosettacode.org/wiki/Empty_directory | Empty directory | Starting with a path to some directory, determine whether the directory is empty.
An empty directory contains no files nor subdirectories.
With Unix or Windows systems, every directory contains an entry for “.” and almost every directory contains “..” (except for a root directory); an empty directory contains no other... | #Go | Go | package main
import (
"fmt"
"io/ioutil"
"log"
)
func main() {
empty, err := IsEmptyDir("/tmp")
if err != nil {
log.Fatalln(err)
}
if empty {
fmt.Printf("/tmp is empty\n")
} else {
fmt.Printf("/tmp is not empty\n")
}
}
func IsEmptyDir(name string) (bool, error) {
entries, err := ioutil.ReadDir(name... |
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