Pick random element
You are encouraged to solve this task according to the task description, using any language you may know.
Demonstrate how to pick a random element from a list.
ACL2
<lang Lisp>:set-state-ok t
(defun pick-random-element (xs state)
(mv-let (idx state) (random$ (len xs) state) (mv (nth idx xs) state)))</lang>
Ada
The following program generates three 20-letter words. Each vowel and each consonant is picked randomly from a list of vowels resp. a list of consonants.
<lang Ada>with Ada.Text_IO, Ada.Numerics.Float_Random;
procedure Pick_Random_Element is
package Rnd renames Ada.Numerics.Float_Random; Gen: Rnd.Generator; -- used globally
type Char_Arr is array (Natural range <>) of Character;
function Pick_Random(A: Char_Arr) return Character is -- Chooses one of the characters of A (uniformly distributed) begin return A(A'First + Natural(Rnd.Random(Gen) * Float(A'Last))); end Pick_Random;
Vowels : Char_Arr := ('a', 'e', 'i', 'o', 'u'); Consonants: Char_Arr := ('t', 'n', 's', 'h', 'r', 'd', 'l'); Specials : Char_Arr := (',', '.', '?', '!');
begin
Rnd.Reset(Gen); for J in 1 .. 3 loop for I in 1 .. 10 loop Ada.Text_IO.Put(Pick_Random(Consonants)); Ada.Text_IO.Put(Pick_Random(Vowels)); end loop; Ada.Text_IO.Put(Pick_Random(Specials) & " "); end loop; Ada.Text_IO.New_Line;
end Pick_Random_Element;</lang>
- Output:
horanohesuhodinahiru. desehonirosedisinelo, losihehederidonolahe?
Aime
<lang aime>list l;
l_append(l, 'a'); l_append(l, 'b'); l_append(l, 'c'); l_append(l, 'd'); l_append(l, 'e'); l_append(l, 'f');
o_byte(l[drand(5)]); o_byte('\n');</lang>
ALGOL 68
<lang algol68># pick a random element from an array of strings #
OP PICKRANDOM = ( []STRING list )STRING: BEGIN
INT number of elements = ( UPB list - LWB list ) + 1; INT random element = ENTIER ( next random * ( number of elements ) );
list[ LWB list + random element ]
END; # PICKRANDOM #
- can define additional operators for other types of array #
main: (
[]STRING days = ( "Sunday", "Monday", "Tuesday", "Wednesday" , "Thursday", "Friday", "Saturday" );
print( ( PICKRANDOM days, newline ) )
)</lang>
- Output:
Thursday
App Inventor
App Inventor has the block pick a random item for selecting a random item from a list.
CLICK HERE TO VIEW THE BLOCKS AND ANDROID APP DISPLAY
AppleScript
<lang AppleScript>get some item of [1, "two", pi, "4", 5 > 4, 5 + 1, Sunday]</lang>
- Output:
"two"
AutoHotkey
- True Arrays
<lang AHK>list := ["abc", "def", "gh", "ijklmnop", "hello", "world"] Random, randint, 1, % list.MaxIndex() MsgBox % List[randint]</lang>
- Pseudo-Arrays
<lang AutoHotkey>list := "abc,def,gh,ijklmnop,hello,world" StringSplit list, list, `, Random, randint, 1, %list0% MsgBox % List%randint%</lang>
AWK
<lang AWK>
- syntax: GAWK -f PICK_RANDOM_ELEMENT.AWK
BEGIN {
n = split("Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday",day_of_week,",") srand() x = int(n*rand()) + 1 printf("%s\n",day_of_week[x]) exit(0)
} </lang>
- Output:
GAWK -f PICK_RANDOM_ELEMENT.AWK Sunday GAWK -f PICK_RANDOM_ELEMENT.AWK Monday GAWK -f PICK_RANDOM_ELEMENT.AWK Wednesday GAWK -f PICK_RANDOM_ELEMENT.AWK Tuesday
BaCon
This is simply an application of a ranged random number used as an array index. BaCon has no built in random element selector.
<lang freebasic>' Pick random element OPTION BASE 1 DECLARE words$[6] FOR i = 1 TO 6 : READ words$[i] : NEXT DATA "Alpha", "Beta", "Gamma", "Delta", "Epsilon", "Zeta"
element = RANDOM(6) + 1 PRINT "Chose ", element, ": ", words$[element]</lang>
- Output:
prompt$ ./pick-random-element Chose 2: Beta prompt$ ./pick-random-element Chose 1: Alpha prompt$ ./pick-random-element Chose 5: Epsilon
Bash
<lang Bash># borrowed from github.com/search?q=bashnative
rand() { printf $(( $1 * RANDOM / 32767 )) } rand_element () {
local -a th=("$@") unset th[0] printf $'%s\n' "${th[$(($(rand "${#th[*]}")+1))]}"
}
echo "You feel like a $(rand_element pig donkey unicorn eagle) today"</lang>
BASIC
Note the use of LBOUND
and UBOUND
. This is only necessary for arrays where the lower and upper limits aren't known. In this example, we know they are 0 and 10 respectively, and could have hard-coded those numbers. (For that matter, the "random selection" line could've just been entered as x = INT(RND * 11)
.)
<lang qbasic>'setup DIM foo(10) AS LONG DIM n AS LONG, x AS LONG FOR n = LBOUND(foo) TO UBOUND(foo)
foo(n) = INT(RND*99999)
NEXT RANDOMIZE TIMER
'random selection x = INT(RND * ((UBOUND(foo) - LBOUND(foo)) + 1))
'output PRINT x, foo(x)</lang>
See also: Liberty BASIC, PureBasic, Run BASIC
Commodore BASIC
<lang qbasic>10 DIM A$(9) 20 FOR I=0 TO 9 : READ A$(I) : NEXT 30 X = RND(-TI) : REM 'PLANT A RANDOM SEED' 40 X = INT(RND(1)*10) 50 PRINT A$(X) 60 END 100 DATA ALPHA, BRAVO, CHARLIE, DELTA, ECHO 110 DATA FOXTROT, GOLF, HOTEL, INDIA, JULIETT</lang>
Batch File
Since there is no arrays in Batch File, I will use a 1-based pseudo-array. <lang dos>@echo off setlocal enabledelayedexpansion
::Initializing the pseudo-array... set "pseudo=Alpha Beta Gamma Delta Epsilon" set cnt=0 & for %%P in (!pseudo!) do ( set /a cnt+=1 set "pseudo[!cnt!]=%%P" ) ::Do the random thing... set /a rndInt=%random% %% cnt +1
::Print the element corresponding to rndint... echo.!pseudo[%rndInt%]! pause exit /b</lang>
- Sample Outputs:
Delta Press any key to continue . . . Gamma Press any key to continue . . . Epsilon Press any key to continue . . . Gamma Press any key to continue . . .
BBC BASIC
<lang bbcbasic> DIM list$(5)
list$() = "The", "five", "boxing", "wizards", "jump", "quickly" chosen% = RND(6) PRINT "Item " ; chosen% " was chosen which is '" list$(chosen%-1) "'"</lang>
- Output:
Item 4 was chosen which is 'wizards'
Burlesque
<lang burlesque> blsq ) "ABCDEFG"123456 0 6rn-]!! 'G </lang>
123456 is the random seed. In order to pick another element you have to change the random seed.
C
<lang c>
- include <stdio.h>
- include <stdlib.h>
- include <time.h>
int main(){
char array[] = { 'a', 'b', 'c','d','e','f','g','h','i','j' }; int i; time_t t; srand((unsigned)time(&t)); for(i=0;i<30;i++){
printf("%c\n", array[rand()%10]);
} return 0;
} </lang> Output
a e f h b d g a b f a i b d d g j a f e a e g e i d j a f e a
C++
<lang cpp>#include <iostream>
- include <random>
- include <vector>
int main( ) {
std::vector<int> numbers { 11 , 88 , -5 , 13 , 4 , 121 , 77 , 2 } ; std::random_device seed ; // generator std::mt19937 engine( seed( ) ) ; // number distribution std::uniform_int_distribution<int> choose( 0 , numbers.size( ) - 1 ) ; std::cout << "random element picked : " << numbers[ choose( engine ) ] << " !\n" ; return 0 ;
}</lang>
C#
<lang csharp>using System; using System.Collections.Generic;
class RandomElementPicker {
static void Main() { var list = new List<int>(new[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}); var rng = new Random(); var randomElement = list[rng.Next(list.Count)]; Console.WriteLine("I picked element {0}", randomElement); }
}</lang>
Ceylon
<lang ceylon>import ceylon.random {
DefaultRandom }
shared void run() {
value random = DefaultRandom(); value element = random.nextElement([1, 2, 3, 4, 5, 6]); print(element);
}</lang>
Clojure
<lang Clojure>(rand-nth coll)</lang>
where coll
is some sequential collection. Equivalent to:
<lang Clojure>(nth coll (rand-int (count coll)))</lang>
COBOL
<lang cobol> >>SOURCE FREE IDENTIFICATION DIVISION. PROGRAM-ID. random-element.
DATA DIVISION. WORKING-STORAGE SECTION. 01 nums-area VALUE "123456789".
03 nums PIC 9 OCCURS 9 TIMES.
01 random-idx PIC 9 COMP.
PROCEDURE DIVISION.
COMPUTE random-idx = FUNCTION RANDOM(FUNCTION CURRENT-DATE (9:7)) * 9 + 1 DISPLAY nums (random-idx) .
END PROGRAM random-element.</lang>
CoffeeScript
<lang coffeescript>array = [1,2,3] console.log array[Math.floor(Math.random() * array.length)]</lang>
Common Lisp
<lang lisp>(defvar *list* '(one two three four five))
(print (nth (random (length *list*)) *list*)) (print (nth (random (length *list*)) *list*)) (print (nth (random (length *list*)) *list*))</lang>
- Output:
FIVE THREE ONE
Crystal
<lang Ruby> puts [1, 2, 3, 4, 5].sample(1) </lang>
D
<lang d>import std.stdio, std.random;
void main() {
const items = ["foo", "bar", "baz"]; items[uniform(0, $)].writeln;
}</lang>
Delphi
See #Pascal / Delphi / Free Pascal.
Déjà Vu
<lang dejavu>!print choose [ "one" "two" "chicken" ]</lang>
EchoLisp
<lang lisp> (define (pick-random list)
(list-ref list (random (length list))))
(pick-random (iota 1000)) → 667 (pick-random (iota 1000)) → 179 </lang>
Elena
ELENA 4.x : <lang elena>import extensions;
extension listOp {
randomItem() = self[randomGenerator.eval(self.Length)];
}
public program() {
var item := new int[]{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}; console.printLine("I picked element ",item.randomItem())
}</lang>
Elixir
<lang elixir>iex(1)> list = Enum.to_list(1..20) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] iex(2)> Enum.random(list) 19 iex(3)> Enum.take_random(list,4) [19, 20, 7, 15]</lang>
Erlang
<lang erlang>% Implemented by Arjun Sunel -module(pick_random). -export([main/0]).
main() -> List =[1,2,3,4,5], Index = rand:uniform(length(List)), lists:nth(Index,List). </lang>
Euphoria
<lang euphoria>constant s = {'a', 'b', 'c'} puts(1,s[rand($)])</lang>
Factor
<lang factor>( scratchpad ) { "a" "b" "c" "d" "e" "f" } random . "a"</lang>
Falcon
<lang falcon> lst = [1, 3, 5, 8, 10] > randomPick(lst) </lang>
Fortran
<lang fortran>program pick_random
implicit none
integer :: i integer :: a(10) = (/ (i, i = 1, 10) /) real :: r
call random_seed call random_number(r) write(*,*) a(int(r*size(a)) + 1)
end program</lang>
FreeBASIC
<lang freebasic>' FB 1.05.0 Win64
Dim a(0 To 9) As String = {"Zero", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine"}
Randomize Dim randInt As Integer
For i As Integer = 1 To 5
randInt = Int(Rnd * 10) Print a(randInt)
Next Sleep</lang>
Sample output :
- Output:
Zero Seven Three Nine Three
Free Pascal
See #Pascal / Delphi / Free Pascal.
F#
<lang fsharp>let list = ["a"; "b"; "c"; "d"; "e"] let rand = new System.Random() printfn "%s" list.[rand.Next(list.Length)]</lang>
Gambas
You can run this code. Copy the code, click this link, paste it in and press 'Run !' <lang gambas>Public Sub Main() Dim sList As String[] = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
Print sList[Rand(0, 11)]
End </lang> Output:
May
GAP
<lang gap>a := [2, 9, 4, 7, 5, 3]; Random(a);</lang>
This works with many GAP objects, for instance groups:
<lang gap>Random(SymmetricGroup(20));
(1,4,8,2)(3,12)(5,14,10,18,17,7,16)(9,13)(11,15,20,19)</lang>
Go
<lang go>package main
import (
"fmt" "math/rand" "time"
)
var list = []string{"bleen", "fuligin", "garrow", "grue", "hooloovoo"}
func main() {
rand.Seed(time.Now().UnixNano()) fmt.Println(list[rand.Intn(len(list))])
}</lang>
Groovy
Solution: <lang groovy>def list = [25, 30, 1, 450, 3, 78] def random = new Random();
(0..3).each {
def i = random.nextInt(list.size()) println "list[${i}] == ${list[i]}"
}</lang>
- Output:
list[3] == 450 list[2] == 1 list[5] == 78 list[3] == 450
Alternate Solution: <lang groovy> [25, 30, 1, 450, 3, 78].sort{new Random()}?.take(1)[0] </lang>
Haskell
Creating a custom function:
<lang haskell>import System.Random (randomRIO)
pick :: [a] -> IO a pick xs = fmap (xs !!) $ randomRIO (0, length xs - 1)
x <- pick [1, 2, 3]</lang>
Using the random-fu library:
<lang haskell>import Data.Random sample $ randomElement [1, 2, 3]</lang>
For example: <lang haskell>do
x <- sample $ randomElement [1, 2, 3] print x</lang>
Icon and Unicon
The unary operator '?' selects a random element from its argument which may be a string, list, table, or set.
<lang Icon>procedure main()
L := [1,2,3] # a list x := ?L # random element
end</lang>
J
<lang j> ({~ ?@#) 'abcdef' b</lang>
Java
<lang java>import java.util.Random; ... int[] array = {1,2,3}; return array[new Random().nextInt(array.length)]; // if done multiple times, the Random object should be re-used</lang>
For a List object rather than an array, substitute list.get(...)
for array[...]
. If preserving the order of the List isn't important, you could call Collections.shuffle(list);
and then list.get(0);
. You would need to shuffle each time unless you remove
d the item from the list.
JavaScript
<lang javascript>var array = [1,2,3]; return array[Math.floor(Math.random() * array.length)];</lang>
Julia
<lang julia>array = [1,2,3] rand(array)</lang>
K
<lang K> 1?"abcdefg" ,"e"</lang>
Kotlin
<lang scala>// version 1.2.10
import java.util.Random
/**
* Extension function on any list that will return a random element from index 0 * to the last index */
fun <E> List<E>.getRandomElement() = this[Random().nextInt(this.size)]
/**
* Extension function on any list that will return a list of unique random picks * from the list. If the specified number of elements you want is larger than the * number of elements in the list it returns null */
fun <E> List<E>.getRandomElements(numberOfElements: Int): List<E>? {
if (numberOfElements > this.size) { return null } return this.shuffled().take(numberOfElements)
}
fun main(args: Array<String>) {
val list = listOf(1, 16, 3, 7, 17, 24, 34, 23, 11, 2) println("The list consists of the following numbers:\n${list}") // notice we can call our extension functions as if they were regular member functions of List println("\nA randomly selected element from the list is ${list.getRandomElement()}") println("\nA random sequence of 5 elements from the list is ${list.getRandomElements(5)}")
}</lang>
Sample output:
- Output:
The list consists of the following numbers: [1, 16, 3, 7, 17, 24, 34, 23, 11, 2] A randomly selected element from the list is 11 A random sequence of 5 elements from the list is [17, 24, 23, 16, 3]
LabVIEW
This image is a VI Snippet, an executable image of LabVIEW code. The LabVIEW version is shown on the top-right hand corner. You can download it, then drag-and-drop it onto the LabVIEW block diagram from a file browser, and it will appear as runnable, editable code.
Lasso
<lang Lasso>local( my array = array('one', 'two', 3) )
- myarray -> get(integer_random(#myarray -> size, 1))</lang>
-> two
Liberty BASIC
The natural way to hold an array of text is in a space- or comma-delimited string, although an array could be used. <lang lb>list$ ="John Paul George Ringo Peter Paul Mary Obama Putin" wantedTerm =int( 10 *rnd( 1)) print "Selecting term "; wantedTerm; " in the list, which was "; word$( list$, wantedTerm, " ")</lang>
Selecting term 5 in the list, which was Peter
LiveCode
<lang LiveCode>put "Apple,Banana,Peach,Apricot,Pear" into fruits put item (random(the number of items of fruits)) of fruits</lang>
Logo
<lang logo>pick [1 2 3]</lang>
Lua
<lang lua>math.randomseed(os.time()) local a = {1,2,3} print(a[math.random(1,#a)])</lang>
Maple
<lang maple>a := [bear, giraffe, dog, rabbit, koala, lion, fox, deer, pony]: randomNum := rand(1 ..numelems(a)): a[randomNum()];</lang>
Mathematica
<lang Mathematica>RandomChoice[{a, b, c}] ->c</lang>
MATLAB / Octave
In case list is a cell array: <lang Matlab> list = {'a','b','c'}; list{ceil(rand(1)*length(list))}</lang>
If list is a vector: <lang Matlab> list = 1:1000; list(ceil(rand(1)*length(list)))</lang>
Maxima
<lang Maxima>random_element(l):= part(l, 1+random(length(l))); /* (%i1) random_element(['a, 'b, 'c]);
(%o1) c
- /</lang>
МК-61/52
<lang>0 П0 1 П1 2 П2 3 П3 4 П4 5
^ СЧ * [x] ПE КИПE С/П</lang>
NetLogo
<lang NetLogo>;; from list containnig only literals and literal constants user-message one-of [ 1 3 "rooster" blue ]
- from list containing variables and reporters
user-message one-of (list (red + 2) turtles (patch 0 0) )</lang>
NetRexx
<lang netrexx>/* NetRexx */ options replace format comments java crossref savelog symbols nobinary
iArray = [ 1, 2, 3, 4, 5 ] -- a traditional array iList = Arrays.asList(iArray) -- a Java Collection "List" object iWords = '1 2 3 4 5' -- a list as a string of space delimited words
v1 = iArray[Random().nextInt(iArray.length)]
v2 = iList.get(Random().nextInt(iList.size()))
v3 = iWords.word(Random().nextInt(iWords.words()) + 1) -- the index for word() starts at one
say v1 v2 v3 </lang>
NewLISP
<lang NewLISP> (define (pick-random-element R) (nth (rand (length R)) R)) </lang> Example:
(setq X '("alpha" "beta" "gamma" "delta" "epsilon")) (println (pick-random-element X)) (println (pick-random-element X)) (println (pick-random-element X)) (println (pick-random-element X))
Nim
<lang nim>randomize()
let ls = @["foo", "bar", "baz"] echo ls.rand()</lang>
Objeck
<lang objeck>values := [1, 2, 3]; value := values[(Float->Random() * 100.0)->As(Int) % values->Size()];</lang>
OCaml
With a list: <lang ocaml>let list_rand lst =
let len = List.length lst in List.nth lst (Random.int len)</lang>
# list_rand [1;2;3;4;5] ;; - : int = 3
With an array: <lang ocaml>let array_rand ary =
let len = Array.length ary in ary.(Random.int len)</lang>
# array_rand [|1;2;3;4;5|] ;; - : int = 3
Oforth
<lang Oforth>: pickRand(l) l size rand l at ;</lang>
Ol
<lang scheme> (import (otus random!))
(define x '("Monday" "Tuesday" "Wednesday" "Thursday" "Friday" "Saturday" "Sunday")) (print (list-ref x (rand! (length x)))) </lang>
PARI/GP
<lang parigp>pick(v)=v[random(#v)+1]</lang>
Pascal / Delphi / Free Pascal
<lang pascal>Program PickRandomElement (output);
const
s: array [1..5] of string = ('1234', 'ABCDE', 'Charlie', 'XB56ds', 'lala');
begin
randomize; writeln(s[low(s) + random(length(s))]);
end.</lang>
Perl
<lang perl>my @array = qw(a b c); print $array[ rand @array ];</lang>
Perl 6
In a nutshell, picking an element from a list is implemented with a method conveniently called "pick": <lang perl6>say (1, 2, 3).pick;</lang>
There are various ways of doing something similar, though. Perl 6 has actually two methods (with associated functional forms) to return random elements depending on whether you are doing selection with or without replacement.
Selection with replacement: (roll of a die) <lang perl6>say (1..6).roll; # return 1 random value in the range 1 through 6 say (1..6).roll(3); # return a list of 3 random values in the range 1 through 6 say (1..6).roll(*)[^100]; # return first 100 values from a lazy infinite list of random values in the range 1 through 6</lang>
Selection without replacement: (pick a card from a deck) <lang perl6># define the deck my @deck = <2 3 4 5 6 7 8 9 J Q K A> X~ <♠ ♣ ♥ ♦>; say @deck.pick; # Pick a card say @deck.pick(5); # Draw 5 say @deck.pick(*); # Get a shuffled deck</lang> Or you can always use the normal rand built-in to generate a subscript (which automatically truncates any fractional part): <lang perl6>@array[@array * rand]</lang> However, the pick and roll methods (not to be confused with the pick-and-roll method in basketball) are more general insofar as they may be used on any enumerable type: <lang perl6>say Bool.pick; # returns either True or False</lang>
Phix
<lang Phix>constant s = {'a','b','c'} puts(1,s[rand(length(s))])</lang>
PHP
<lang php>$arr = array('foo', 'bar', 'baz'); $x = $arr[array_rand($arr)];</lang>
PicoLisp
<lang PicoLisp>(get Lst (rand 1 (length Lst)))</lang>
PL/I
<lang pli> declare t(0:9) character (1) static initial
('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'); put ( t(10*random()) );</lang>
- Output:
e
Powershell
Powershell has Get-Random Cmdlet which one of its overload is to select randomly from a given list
<lang Powershell> 1..100 | Get-Random -Count 3 </lang>
Prolog
<lang prolog> ?- random_member(M, [a, b, c, d, e, f, g, h, i, j]). M = i. </lang>
PureBasic
<lang PureBasic>Procedure.s pickRandomElement(List source.s())
Protected x = ListSize(source()) If x > 0 SelectElement(source(), Random(x - 1)) ;element numbering is zero - based ProcedureReturn source() EndIf
EndProcedure
- initialize list elements
DataSection
elements: Data.s "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"
EndDataSection
- elementCount = 10
NewList item.s()
Restore elements Define i For i = 1 To #elementCount
AddElement(item()) Read.s item()
Next
If OpenConsole()
Print("Source list: ") ForEach item() Print(item() + " ") Next PrintN(#CRLF$) Print("Random picks from list: ") For i = 1 To 10 Print(pickRandomElement(item()) + " ") Next Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input() CloseConsole()
EndIf</lang>
- Output:
Source list: One Two Three Four Five Six Seven Eight Nine Ten Random picks from list: Seven Nine Two Six Four Four Nine Three Six Two
Easy version
<lang purebasic>OpenConsole()
a$="One" +#TAB$+ "Two" +#TAB$+ "Three" +#TAB$+ "Four" +#TAB$+ "Five" +#TAB$+
"Six" +#TAB$+ "Seven"+#TAB$+ "Eight" +#TAB$+ "Nine" +#TAB$+ "Ten" +#TAB$
Print("Source list: "+#TAB$+a$+#CRLF$+"Random list: "+#TAB$)
For i=1 To CountString(a$,#TAB$)
Print(StringField(a$,Random(CountString(a$,#TAB$),1),#TAB$)+#TAB$)
Next Input()</lang>
- Output:
Source list: One Two Three Four Five Six Seven Eight Nine Ten Random list: One Two Seven Nine Ten Seven Three Five Ten Nine
Python
<lang python>>>> import random >>> random.choice(['foo', 'bar', 'baz']) 'baz'</lang>
R
<lang rsplus># a vector (letters are builtin) letters
- [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s"
- [20] "t" "u" "v" "w" "x" "y" "z"
- picking one element
sample(letters, 1)
- [1] "n"
- picking some elements with repetition, and concatenating to get a word
paste(sample(letters, 10, rep=T), collapse="")
- [1] "episxgcgmt"</lang>
Racket
<lang Racket>
- lang racket
(define (pick-item l)
(list-ref l (random (length l))))
</lang>
REXX
version 1
This REXX example takes the Rosetta Code task very literally. <lang rexx>/*REXX program picks a random element from a list (tongue in cheek, a visual pun).*/ _= 'hydrogen helium lithium beryllium boron carbon nitrogen oxygen fluorine neon sodium' _=_ 'magnesium aluminum silicon phosphorous sulfur chlorine argon potassium calcium' _=_ 'scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium' _=_ 'germanium arsenic selenium bromine krypton rubidium strontium yttrium zirconium' _=_ 'niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin' _=_ 'antimony tellurium iodine xenon cesium barium lanthanum cerium praseodymium' _=_ 'neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium' _=_ 'thulium ytterbium lutetium hafnium tantalum tungsten rhenium osmium iridium platinum' _=_ 'gold mercury thallium lead bismuth polonium astatine radon francium radium actinium' _=_ 'thorium protactinium uranium neptunium plutonium americium curium berkelium' _=_ 'californium einsteinium fermium mendelevium nobelium lawrencium rutherfordium dubnium' _=_ 'seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium Ununtrium'
- =words(_) /*obtain the number of words in list. */
item=subword(_, random(1, #), 1) /*obtain random word (element) in list.*/ say 'random element: ' item /*stick a fork in it, we're all done. */</lang>
- output:
random element: copernicium
version 2
Slightly simplified:
Note that this version doesn't work (receives a syntax error 12) with REXXes that have a
smaller limit of the total length of a clause, in particular PC/REXX and Personal REXX
which have a limit of 1,000 characters).
<lang rexx>
/* REXX ***************************************************************
- 18.10.2012 Walter Pachl Not only the list of elements shortened:-)
- /
wl='hydrogen helium lithium beryllium boron carbon nitrogen oxygen',
'fluorine neon sodium magnesium aluminum silicon phosphorous sulfur', '...', 'meitnerium darmstadtium roentgenium copernicium Ununtrium'
Say word(wl,random(1,words(wl))) </lang>
Red
<lang Red>>> random/only collect [repeat i 10 [keep i]]</lang>
Ring
<lang ring> aList = "abcdefghij" for i = 1 to 10
letter = random(9) + 1 if letter > 0 see aList[letter] + nl ok
next </lang>
Ruby
<lang ruby> %w(north east south west).sample # => "west" (1..100).to_a.sample(2) # => [17, 79]</lang>
Run BASIC
<lang runbasic>list$ = "a,b,c,d,e,f,g,h,i,j" letter = rnd(1) * 10 print "Selected letter:"; word$(list$,letter,",")</lang>
Rust
<lang rust>extern crate rand;
use rand::Rng;
fn main() {
let array = [5,1,2,5,6,7,8,1,2,4,5]; let mut rng = rand::thread_rng(); println!("{}", rng.choose(&array).unwrap());
}</lang>
Scala
<lang Scala>val a = (1 to 10).toList
println(scala.util.Random.shuffle(a).head)</lang>
Seed7
<lang seed7>$ include "seed7_05.s7i";
const proc: main is func
begin writeln(rand([] ("foo", "bar", "baz"))); end func;</lang>
Sidef
<lang ruby>var arr = %w(north east south west); say arr.rand; say arr.rand(2).dump;</lang>
- Output:
south ['west', 'south']
Smalltalk
<lang smalltalk>x := #(1 2 3) atRandom.</lang>
SuperCollider
<lang SuperCollider>[1, 2, 3].choose</lang>
Swift
<lang Swift>import Darwin
let myList = [1, 2, 4, 5, 62, 234, 1, -1] print(myList[Int(arc4random_uniform(UInt32(myList.count)))])</lang>
Tcl
Random selection from a list is implemented by composing lindex
(for selection of an item from a list) and the pattern for generating an integral random number from the range .
It's simpler to use when wrapped up as a helper procedure:
<lang tcl>proc randelem {list} {
lindex $list [expr {int(rand()*[llength $list])}]
} set x [randelem {1 2 3 4 5}]</lang>
TXR
<lang txr>@(do (defun randelem (seq)
[seq (random nil (length seq))]))
@(bind x @(randelem #("a" "b" "c" "d")))</lang>
TUSCRIPT
<lang tuscript>$$ MODE TUSCRIPT list="John'Paul'George'Ringo'Peter'Paul'Mary'Obama'Putin" sizeList=SIZE(list) selectedNr=RANDOM_NUMBERS (1,sizeList,1) selectedItem=SELECT(list,#selectednr) PRINT "Selecting term ",selectedNr," in the list, which was ",selectedItem</lang>
- Output:
Selecting term 3 in the list, which was George
Ursa
<lang ursa># generate a stream (ursa equivalent of a list) decl string<> str append "these" "are" "some" "values" str
decl ursa.util.random r out str<(r.getint (size str))> endl console</lang>
VBA
<lang vb> Option Explicit
Sub Main_Pick_Random_Element()
Debug.Print Pick_Random_Element(Array(1, 2, 3, 4, 5, #11/24/2017#, "azerty"))
End Sub
Function Pick_Random_Element(myArray)
Randomize Timer Pick_Random_Element = myArray(Int((Rnd * (UBound(myArray) - LBound(myArray) + 1) + LBound(myArray))))
End Function </lang>
VBScript
<lang vb> Function pick_random(arr) Set objRandom = CreateObject("System.Random") pick_random = arr(objRandom.Next_2(0,UBound(arr)+1)) End Function
WScript.Echo pick_random(Array("a","b","c","d","e","f")) </lang>
- Output:
d
XPL0
<lang XPL0>code Ran=1, Text=12; int List; [List:= ["hydrogen", "helium", "lithium", "beryllium", "boron"]; \(Thanks REXX) Text(0, List(Ran(5))); ]</lang>
zkl
<lang zkl>list:=T("hydrogen", "helium", "lithium", "beryllium", "boron"); list[(0).random(list.len())]</lang>
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