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Show a loop which prints random numbers (each number newly generated each loop) from 0 to 19 (inclusive). If a number is 10, stop the loop after printing it, and do not generate any further numbers. Otherwise, generate and print a second random number before restarting the loop. If the number 10 is never generated as the first number in a loop, loop forever.

6502 Assembly

Code is called as a subroutine (i.e. JSR LoopBreakSub). Specific OS/hardware routines for generating random numbers and printing are left unimplemented. <lang 6502asm>LoopBreakSub: PHA ;push accumulator onto stack

BreakLoop: JSR GenerateRandomNum ;routine not implemented ;generates random number and puts in memory location RandomNumber

LDA RandomNumber JSR DisplayAccumulator ;routine not implemented CMP #10 BEQ Break JSR GenerateRandomNum LDA RandomNumber JSR DisplayAccumulator JMP BreakLoop

Break: PLA ;restore accumulator from stack RTS ;return from subroutine</lang>

Ada

<lang Ada>with Ada.Text_IO; use Ada.Text_IO; with Ada.Numerics.Discrete_Random;

procedure Test_Loop_Break is

  type Value_Type is range 0..19;
  package Random_Values is new Ada.Numerics.Discrete_Random (Value_Type);
  use Random_Values;
  Dice : Generator;
  A, B : Value_Type;

begin

  loop
     A := Random (Dice);
     Put_Line (Value_Type'Image (A));
     exit when A = 10;
     B := Random (Dice);
     Put_Line (Value_Type'Image (B));
  end loop;

end Test_Loop_Break;</lang>

Aime

<lang aime>integer main(void) {

   integer a, b;

   while (1) {
       a = drand(19);
       o_integer(a);
       o_byte('\n');
       if (a == 10) {
           break;
       }

       b = drand(19);
       o_integer(b);
       o_byte('\n');
   }

   return 0;

}</lang>

ALGOL 68

Translation of: C – Note: This specimen retains the original C coding style.

Works with: ALGOL 68 version Standard - no extensions to language used

Works with: ELLA ALGOL 68 version Any (with appropriate job cards)

<lang algol68>main: (

   INT a, b;
   INT seed := 4; # chosen by a fair dice roll, guaranteed to be random c.f. http://xkcd.com/221/ #
   # first random; #
   WHILE
       a := ENTIER (next random(seed) * 20);
       print((a));
 # WHILE # NOT (a = 10) DO
       b := ENTIER (next random(seed) * 20);
       print((b, new line))
   OD;
   print(new line)

)</lang>

Output:

        +13          +6
         +1          +8
        +13          +2
         +1         +12
         +0         +12
        +14          +8
         +9          +2
        +19         +13
         +0          +4
         +8         +14
        +17          +7
        +11          +9
         +7          +8
         +2          +1
        +11          +2
        +13         +18
         +3          +7
        +11         +17
         +4         +13
        +16         +12
        +19         +17
         +9          +7
         +8          +5
         +4          +8
         +7          +5
         +0         +18
         +8         +13
         +7          +4
        +10

AppleScript

<lang AppleScript>repeat set a to random number from 0 to 19 if a is 10 then log a exit repeat end if set b to random number from 0 to 19 log a & b end repeat</lang>

Output:

(*12, 6*)
(*7, 8*)
(*17, 4*)
(*7, 2*)
(*0, 5*)
(*6, 3*)
(*5, 5*)
(*3, 14*)
(*7, 7*)
(*3, 11*)
(*5, 16*)
(*18, 2*)
(*5, 2*)
(*15, 17*)
(*16, 10*)
(*4, 18*)
(*8, 5*)
(*4, 15*)
(*11, 14*)
(*7, 2*)
(*1, 7*)
(*7, 7*)
(*4, 9*)
(*12, 17*)
(*8, 16*)
(*9, 1*)
(*16, 15*)
(*8, 2*)
(*9, 6*)
(*13, 6*)
(*17, 0*)
(*17, 18*)
(*4, 7*)
(*8, 10*)
(*11, 0*)
(*14, 17*)
(*9, 8*)
(*2, 17*)
(*1, 5*)
(*4, 5*)
(*5, 2*)
(*10*)

AutoHotkey

<lang AutoHotkey>Loop {

 Random, var, 0, 19
 output = %output%`n%var%
 If (var = 10)
   Break
 Random, var, 0, 19
 output = %output%`n%var%

} MsgBox % output</lang>

AWK

<lang awk>BEGIN { for (;;) { print n = int(rand() * 20) if (n == 10) break print int(rand() * 20) } }</lang>

Axe

Because Axe only supports breaking out of loops as end conditions, the behavior must be simulated using a return statement. Note, however, that this will exit the current call context, not the necessarily just the current loop.

<lang axe>While 1

rand^20→A
Disp A▶Dec
ReturnIf A=10
rand^20→B
Disp B▶Dec,i

End</lang>

BASIC

Works with: QuickBasic version 4.5

<lang qbasic>do

   a = int(rnd * 20)
   print a
   if a = 10 then exit loop 'EXIT FOR works the same inside FOR loops
   b = int(rnd * 20)
   print b

loop</lang>

ZX Spectrum Basic

On the ZX Spectrum, for loops must be terminated through the NEXT statement, otherwise a memory leak will occur. To terminate a loop prematurely, set the loop counter to the last iterative value and jump to the NEXT statement:

<lang zxbasic>10 FOR l = 1 TO 20 20 IF l = 10 THEN LET l = 20: GO TO 40: REM terminate the loop 30 PRINT l 40 NEXT l 50 STOP</lang>

The correct solution:

<lang zxbasic>10 LET a = INT (RND * 20) 20 PRINT a 30 IF a = 10 THEN STOP 40 PRINT INT (RND * 20) 50 GO TO 10</lang>

Batch File

<lang dos>@echo off

loop

 set /a N=%RANDOM% %% 20
 echo %N%
 if %N%==10 exit /b
 set /a N=%RANDOM% %% 20
 echo %N%

goto loop</lang>

BBC BASIC

Works with: BBC BASIC for Windows

<lang bbcbasic> REPEAT

       num% = RND(20)-1
       PRINT num%
       IF num%=10 THEN EXIT REPEAT
       PRINT RND(20)-1
     UNTIL FALSE</lang>

bc

<lang bc>s = 1 /* seed of the random number generator */ scale = 0

/* Random number from 0 to 20. */ define r() { auto a while (1) { /* Formula (from POSIX) for random numbers of low quality. */ s = (s * 1103515245 + 12345) % 4294967296 a = s / 65536 /* a in [0, 65536) */ if (a >= 16) break /* want a >= 65536 % 20 */ } return (a % 20) }

while (1) { n = r() n /* print 1st number */ if (n == 10) break r() /* print 2nd number */ } quit</lang>

C

<lang c>#include <stdlib.h>

include <time.h>
include <stdio.h>

define LOWER 0
define UPPER 19

int main() {

   srand(time(NULL));
   
   for (;;) {
       unsigned a = LOWER + rand() / (RAND_MAX / (UPPER - LOWER + 1) + 1);
       printf("%d\n", a);
       if (a == 10) break;
   }
   return 0;

} </lang>

C#

<lang csharp>class Program {

   static void Main(string[] args)
   {
       Random random = new Random();
       while (true)
       {
           int a = random.Next(20);
           Console.WriteLine(a);
           if (a == 10)
               break;
           int b = random.Next(20)
           Console.WriteLine(b);
       }
          
       Console.ReadLine();
   }

}</lang>

C++

<lang cpp>#include <iostream>

include <ctime>
include <cstdlib>

int main() {

   srand(time(0));
   while(true)
   {
   	int a = 0 + rand() % 19;
   	std::cout << a << std::endl;
   	if (a == 10)
   		break;
   	int b = 0 + rand() % 19;
   	std::cout << b << std::endl;
   }
   return 0;

}</lang>

Chapel

<lang chapel>use Random;

var r = new RandomStream(); while true {

       var a = floor(r.getNext() * 20):int;
       writeln(a);
       if a == 10 then break;
       var b = floor(r.getNext() * 20):int;
       writeln(b);

} delete r;</lang>

Chef

"Liquify" is now depreciated in favor of "Liquefy", but my interpreter/compiler (Acme::Chef) works only with "Liquify" so that's how I'm leaving it. At least it'll work no matter which version you use.

<lang Chef>Healthy Vita-Sauce Loop - Broken.

Makes a whole lot of sauce for two people.

Ingredients. 0 g Vitamin A 1 g Vitamin B 2 g Vitamin C 3 g Vitamin D 4 g Vitamin E 5 g Vitamin F 6 g Vitamin G 7 g Vitamin H 8 g Vitamin I 9 g Vitamin J 10 g Vitamin K 11 g Vitamin L 12 g Vitamin M 13 g Vitamin N 14 g Vitamin O 15 g Vitamin P 16 g Vitamin Q 17 g Vitamin R 18 g Vitamin S 19 g Vitamin T 20 g Vitamin U 21 g Vitamin V 22 g Vitamin W 32 g Vitamin X 24 g Vitamin Y 25 g Vitamin Z

Method. Liquify Vitamin X. Put Vitamin N into 1st mixing bowl. Fold Vitamin Y into 1st mixing bowl. Liquify Vitamin Y. Clean 1st mixing bowl. Put Vitamin K into 1st mixing bowl. Fold Vitamin Z into 1st mixing bowl. Liquify Vitamin Z. Clean 1st mixing bowl. Put Vitamin Y into 4th mixing bowl. Put Vitamin Z into 4th mixing bowl. Pour contents of the 4th mixing bowl into the 2nd baking dish. Put Vitamin A into 2nd mixing bowl. Put Vitamin B into 2nd mixing bowl. Put Vitamin C into 2nd mixing bowl. Put Vitamin D into 2nd mixing bowl. Put Vitamin E into 2nd mixing bowl. Put Vitamin F into 2nd mixing bowl. Put Vitamin G into 2nd mixing bowl. Put Vitamin H into 2nd mixing bowl. Put Vitamin I into 2nd mixing bowl. Put Vitamin J into 2nd mixing bowl. Put Vitamin K into 2nd mixing bowl. Put Vitamin L into 2nd mixing bowl. Put Vitamin M into 2nd mixing bowl. Put Vitamin N into 2nd mixing bowl. Put Vitamin O into 2nd mixing bowl. Put Vitamin P into 2nd mixing bowl. Put Vitamin Q into 2nd mixing bowl. Put Vitamin R into 2nd mixing bowl. Put Vitamin S into 2nd mixing bowl. Put Vitamin T into 2nd mixing bowl. Verb the Vitamin V. Mix the 2nd mixing bowl well. Fold Vitamin U into 2nd mixing bowl. Put Vitamin U into 3rd mixing bowl. Remove Vitamin K from 3rd mixing bowl. Fold Vitamin V into 3rd mixing bowl. Put Vitamin X into 1st mixing bowl. Put Vitamin V into 1st mixing bowl. Verb until verbed. Pour contents of the 1st mixing bowl into the 1st baking dish.

Serves 2.</lang>

Clojure

<lang lisp>(loop [[a b & more] (repeatedly #(rand-int 20))]

 (println a)
 (when-not (= 10 a) 
   (println b) 
   (recur more)))</lang>

COBOL

Works with: OpenCOBOL

<lang cobol> IDENTIFICATION DIVISION.

      PROGRAM-ID. Random-Nums.

      DATA DIVISION.
      WORKING-STORAGE SECTION.
      01  Num  PIC Z9.

      PROCEDURE DIVISION.
      Main.
          PERFORM FOREVER
              PERFORM Generate-And-Display-Num

              IF Num = 10
                  EXIT PERFORM
              ELSE
                  PERFORM Generate-And-Display-Num
              END-IF
          END-PERFORM

          GOBACK
          .

      Generate-And-Display-Num.
          COMPUTE Num =  FUNCTION REM(FUNCTION RANDOM * 100, 20)
          DISPLAY Num
          .</lang>

CoffeeScript

We can use print from the Rhino JavaScript shell as in the JavaScript example or console.log, with a result like this: <lang coffeescript> loop

 print a = Math.random() * 20 // 1  
 break if a == 10
 print Math.random() * 20 // 1

</lang>

ColdFusion

 <Cfset randNum = RandRange(0, 19)>
 <Cfoutput>#randNum#</Cfoutput>
 <Cfif randNum eq 10><cfbreak></Cfif>
 <Cfoutput>#RandRange(0, 19)#</Cfoutput>

</cfloop> </lang>

Output:

My first two test outputs (I swear this is true)

Common Lisp

<lang lisp>(loop for a = (random 20)

     do (print a)
     until (= a 10)
     do (print (random 20)))</lang>

D

<lang d>import std.stdio, std.random;

void main() {

   while (true) {
       int r = uniform(0, 20);
       write(r, " ");
       if (r == 10)
           break;
       write(uniform(0, 20), " ");
   }

}</lang>

Output:

2 4 9 5 3 7 4 4 14 14 3 7 13 8 13 6 10

dc

Translation of: bc

<lang dc>1 ss [s = seed of the random number generator]sz 0k [scale = 0]sz

[Function r: Push a random number from 0 to 20.]sz [

[2Q]SA
[
 [Formula (from POSIX) for random numbers of low quality.]sz
 ls 1103515245 * 12345 + 4294967296 % d ss  [Compute next s]sz
 65536 /     [it = s / 65536]sz
 d 16 !>A    [Break loop if 16 <= it]sz
 sz 0 0 =B   [Forget it, continue loop]sz
]SB 0 0 =B
20 %         [Push it % 20]sz
LA sz LB sz  [Restore A, B]sz

]sr

[2Q]sA [

0 0 =r p     [Print 1st number.]sz
10 =A        [Break if 10 == it.]sz
0 0 =r p sz  [Print 2nd number.]sz
0 0 =B       [Continue loop.]sz

]sB 0 0 =B</lang>

Delphi

<lang Delphi>program Project5;

{$APPTYPE CONSOLE}

var

 num:Integer;

begin

 Randomize;
 while true do
 begin
   num:=Random(20);
   Writeln(num);
   if num=10 then break;
 end;

end.

</lang>

DWScript

<lang delphi> while True do begin

  var num := RandomInt(20);
  PrintLn(num);
  if num=10 then Break;

end;</lang>

E

<lang e>while (true) {

   def a := entropy.nextInt(20)
   print(a)
   if (a == 10) {
       println()
       break
   }
   println(" ", entropy.nextInt(20))

}</lang>

Ela

This implementation uses .NET Framework Math.Randomize function. Current ticks multiplied by an iteration index are used as a seed. As a result, an output looks almost truly random:

<lang ela>open datetime random monad io

loop = loop' 1

      where loop' n t = do
               dt <- datetime.now
               seed <- return <| toInt <| (ticks <| dt) * n
               r <- return $ rnd seed 0 19
               putStrLn (show r)
               if r <> t then loop' (n + 1) t else return ()

loop 10 ::: IO</lang>

Elixir

<lang elixir>defmodule Loops do

 def break do
   :random.seed(:os.timestamp)
   break(:random.uniform(20)-1)
 end
 
 def break(10), do: IO.puts 10
 def break(r) do
   IO.write r
   IO.puts ",\t#{:random.uniform(20)-1}"
   break(:random.uniform(20)-1)
 end

end

Loops.break</lang>

Output:

Erlang

<lang erlang>%% Implemented by Arjun Sunel -module(forever). -export([main/0, for/0]).

main() -> for().

for() -> K = random:uniform(19),

       io:fwrite( "~p ", [K] ),

if K==10 -> ok; true -> M = random:uniform(19), io:format("~p~n",[M]),

  		for()

end. </lang>

ERRE

<lang ERRE> LOOP

   A=INT(RND(1)*20)
   PRINT(A)
   IF A=10 THEN EXIT LOOP END IF !EXIT FOR works the same inside FOR loops
   PRINT(INT(RND(1)*20))

END LOOP </lang> The RND(X) function returns a random integer from 0 to 1. X is a dummy argument.

Euphoria

<lang euphoria>integer i while 1 do

   i = rand(20) - 1
   printf(1, "%g ", {i})
   if i = 10 then
       exit
   end if
   printf(1, "%g ", {rand(20)-1})

end while</lang> The rand() function returns a random integer from 1 to the integer provided.

Factor

Using with-return: <lang factor>[

   [ 20 random [ . ] [ 10 = [ return ] when ] bi 20 random . t ] loop

] with-return</lang>

Idiomatic Factor: <lang factor>[ 20 random [ . ] [ 10 = not ] bi dup [ 20 random . ] when ] loop</lang>

Fantom

<lang fantom> class ForBreak {

 public static Void main ()
 {
   while (true)
   {
     a := Int.random(0..19)
     echo (a)
     if (a == 10) break
     echo (Int.random(0..19))
   }
 }

} </lang>

Forth

<lang forth>include random.fs

main

 begin  20 random dup . 10 <>
 while  20 random .
 repeat ;

\ use LEAVE to break out of a counted loop

main

 100 0 do
   i random dup .
   10 = if leave then
   i random .
 loop ;</lang>

Fortran

Works with: Fortran version 90 and later

<lang fortran>program Example

 implicit none

 real :: r
 integer :: a, b

 do
    call random_number(r)
    a = int(r * 20)
    write(*,*) a
    if (a == 10) exit
    call random_number(r)
    b = int(r * 20)
    write(*,*) b
 end do

end program Example</lang>

Works with: Fortran version 77 and later

<lang fortran> PROGRAM LOOPBREAK

       INTEGER I, RNDINT

C It doesn't matter what number you put here.

       CALL SDRAND(123)

C Because FORTRAN 77 semantically lacks many loop structures, we C have to use GOTO statements to do the same thing.

  10   CONTINUE

C Print a random number.

         I = RNDINT(0, 19)
         WRITE (*,*) I

C If the random number is ten, break (i.e. skip to after the end C of the "loop").

         IF (I .EQ. 10) GOTO 20

C Otherwise, print a second random number.

         I = RNDINT(0, 19)
         WRITE (*,*) I

C This is the end of our "loop," meaning we jump back to the C beginning again.

         GOTO 10

  20   CONTINUE

       STOP
     END

C FORTRAN 77 does not come with a random number generator, but it C is easy enough to type "fortran 77 random number generator" into your C preferred search engine and to copy and paste what you find. The C following code is a slightly-modified version of: C C http://www.tat.physik.uni-tuebingen.de/ C ~kley/lehre/ftn77/tutorial/subprograms.html

     SUBROUTINE SDRAND (IRSEED)
       COMMON  /SEED/ UTSEED, IRFRST
       UTSEED = IRSEED
       IRFRST = 0
       RETURN
     END
     INTEGER FUNCTION RNDINT (IFROM, ITO)
       INTEGER IFROM, ITO
       PARAMETER (MPLIER=16807, MODLUS=2147483647,                     &
    &              MOBYMP=127773, MOMDMP=2836)
       COMMON  /SEED/ UTSEED, IRFRST
       INTEGER HVLUE, LVLUE, TESTV, NEXTN
       SAVE    NEXTN
       IF (IRFRST .EQ. 0) THEN
         NEXTN = UTSEED
         IRFRST = 1
       ENDIF
       HVLUE = NEXTN / MOBYMP
       LVLUE = MOD(NEXTN, MOBYMP)
       TESTV = MPLIER*LVLUE - MOMDMP*HVLUE
       IF (TESTV .GT. 0) THEN
         NEXTN = TESTV
       ELSE
         NEXTN = TESTV + MODLUS
       ENDIF
       IF (NEXTN .GE. 0) THEN
         RNDINT = MOD(MOD(NEXTN, MODLUS), ITO - IFROM + 1) + IFROM
       ELSE
         RNDINT = MOD(MOD(NEXTN, MODLUS), ITO - IFROM + 1) + ITO + 1
       ENDIF
       RETURN
     END</lang>

Works with: Fortran version 66 and earlier

Anyone who attempts to produce random numbers via a computation is already in a state of sin, so, one might as well be hung as a goat rather than as a lamb. Here is a version using the RANDU generator, in the style of Fortran 66 as offered by the IBM1130. No logical-if statements and reliance on implicit type declarations. Sixteen-bit integers result. The standard advice is to start IX off as an odd number. Note that RANDU does not update IX (the "seed"); the caller must do so. Since integer overflow producing negative numbers is undone by adding 32768 (trusting that the compiler will not attempt to combine constants, thus + 32767 + 1) in the absence of an AND operation, possible values for IY are presumably zero to 32767. Since IY is divided by 32767.0 (not 32768.0 for example), the range for YFL is zero to one inclusive, though further inspection shows that zero is not attained for proper starts - should IX be zero it will never change, thus the span is (0,1]; a more common arrangement is [0,1).

Because the upper bound is attainable, multiplying YFL by 19 and truncating the result will mean that 19 appears only as an edge event when IY = 32767. Multiplying by 20 will ensure that 19 gets its fair share along with each other integer, but, the edge event might now occasionally produce a 20. There is no MIN function available, so, explicit testing results. Rather than repeat this code with its consequent litter of labels, a helper function IR19 does the work once. These out-by-one opportunities are vexing.

The RANDU routine is so notorious that latter-day compilers can supply their own RANDU (using a better method), and further, disregard a user-supplied RANDU routine so it may have to be called RANDUU or some other name! <lang Fortran>

     SUBROUTINE RANDU(IX,IY,YFL)

Copied from the IBM1130 Scientific Subroutines Package (1130-CM-02X): Programmer's Manual, page 60. CAUTION! This routine's 32-bit variant is reviled by Prof. Knuth and many others for good reason!

       IY = IX*899
       IF (IY) 5,6,6
   5   IY = IY + 32767 + 1
   6   YFL = IY
       YFL = YFL/32767.
     END

     FUNCTION IR19(IX)
       CALL RANDU(IX,IY,YFL)
       IX = IY
       I = YFL*20
       IF (I - 20) 12,11,11
  11   I = 19
  12   IR19 = I
     END

     IX = 1

Commence the loop.

  10 I = IR19(IX)
     WRITE (6,11) I
  11 FORMAT (I3)
     IF (I - 10) 12,20,12
  12 I = IR19(IX)
     WRITE (6,11) I
     GO TO 10

Cease.

  20 CONTINUE
     END

</lang> Output, converted to along the line:

 0 13  4 19  1  7  2 12  4  7 14 11  6  4  0  9  5 12 16 19 18  2  0 13  2  7 10

This source will compile with later compilers (possibly after adding INTEGER*2 declarations to not use larger integers), as well as earlier compilers. But the IBM1620's Fortran II ran on a decimal computer (and the compiler allowed an option to specify how many digits in a number) so the assumption of sixteen-bit two's-complement arithmetic would fail. There was once much more variety in computer design, not just always a power of two in word sizes.

GAP

<lang gap>while true do

   a := Random(0, 19);
   Print(a);
   if a = 10 then
       Print("\n");
       break;
   fi;
   a := Random(0, 19);
   Print("\t", a, "\n");

od;

11 6
5 8
1 4
5 10
1 16
10</lang>

GML

<lang GML>while(1)

   {
   a = floor(random(19))
   show_message(string(a))
   if(a = 10)
       break
   b = floor(random(19))
   show_message(string(a))
   }

</lang>

Go

<lang go>package main

import "fmt" import "math/rand" import "time"

func main() {

   rand.Seed(time.Now().UnixNano())
   for {
       a := rand.Intn(20)
       fmt.Println(a)
       if a == 10 {
           break
       }
       b := rand.Intn(20)
       fmt.Println(b)
   }

}</lang>

Groovy

<lang groovy>final random = new Random()

while (true) {

   def random1 = random.nextInt(20)
   print random1
   if (random1 == 10) break
   print '     '
   println random.nextInt(20)

}</lang>

GW-BASIC

<lang qbasic>10 NUM = 0 20 WHILE NUM <> 10 30 NUM = INT(RND * 20) 40 PRINT NUM 50 WEND</lang>

Harbour

<lang visualfoxpro>PROCEDURE Loop()

  LOCAL n

  DO WHILE .T.
     ? n := hb_RandomInt( 0, 19 )
     IF n == 10
        EXIT
     ENDIF
     ? hb_RandomInt( 0, 19 )
  ENDDO

  RETURN</lang>

Haskell

<lang haskell>import Control.Monad import System.Random

loopBreak n k = do

 r <- randomRIO (0,n)
 print r
 unless (r==k) $ do
   print =<< randomRIO (0,n)
   loopBreak n k</lang>

Use: <lang haskell>loopBreak 19 10</lang>

HicEst

<lang hicest>1 DO i = 1, 1E20 ! "forever"

    a = INT( RAN(10, 10) )
    WRITE(name) a
    IF( a == 10) GOTO 10
    b = INT( RAN(10, 10) )
    WRITE(name) b
  ENDDO

10

END</lang>

Icon and Unicon

<lang Icon>procedure main()

   while 10 ~= writes(?20-1) do write(", ",?20-1)

end</lang> Notes:

For any positive integer i, ?i produces a value j where 1 <= j <= i
Although this can be written with a break (e.g. repeat expression & break), there is no need to actually use one. (And it's ugly).
Programmers new to Icon/Unicon need to understand that just about everything returns values including comparison operators, I/O functions like write/writes.
This program will perform similarly but not identically under Icon and Unicon because the random operator ?i behaves differently. While both produce pseudo-random numbers a different generator is used. Also, the sequence produced by Icon begins with the same seed value and is repeatable whereas the sequence produced by Unicon does not. One way to force Icon to use different random sequences on each call would be to add the line <lang Icon>&random := integer(map("smhSMH","Hh:Mm:Ss",&clock))</lang> at the start of the main procedure to set the random number seed based on the time of day.

J

<lang j>loopexample=: verb define

 while. 1 do.
   smoutput n=. ?20
   if. 10=n do. return. end.
   smoutput ?20
 end.

)</lang>

Note that break. could have been used in place of return..

Java

<lang java>import java.util.Random;

Random rand = new Random(); while(true){

   int a = rand.nextInt(20);
   System.out.println(a);
   if(a == 10) break;
   int b = rand.nextInt(20);
   System.out.println(b);

}</lang>

JavaScript

<lang javascript>for (;;) {

 var a = Math.floor(Math.random() * 20);
 print(a);
 if (a == 10) 
   break;
 a = Math.floor(Math.random() * 20);
 print(a);

}</lang> The print() function is available in the Rhino JavaScript shell.

If we step back for a moment from imperative assumptions about repetitive processes and their interruption, we may notice that there is actually no necessary connection between repetitive process and loops.

In a functional idiom of JavaScript, we might instead write something like:

<lang JavaScript>(function streamTillInitialTen() {

   var nFirst = Math.floor(Math.random() * 20);
       
   console.log(nFirst);
   
   if (nFirst === 10) return true;
   
   console.log(
       Math.floor(Math.random() * 20)
   );
   
   return streamTillInitialTen();

})();</lang>

Obtaining runs like:

Though returning a value composes better, and costs less IO traffic, than firing off side-effects from a moving thread:

<lang JavaScript>console.log(

 (function streamTillInitialTen() {
   var nFirst = Math.floor(Math.random() * 20);
 
   if (nFirst === 10) return [10];
 
   return [
     nFirst,
     Math.floor(Math.random() * 20)
   ].concat(
     streamTillInitialTen()
   );
 })().join('\n')

);</lang>

Sample result:

Julia

<lang Julia> while true

   n = rand(0:19)
   @printf "%4d" n
   if n == 10
       println()
       break
   end
   n = rand(0:19)
   @printf "%4d\n" n

end </lang>

Output:

Kotlin

Translation of: Java

<lang scala>import java.util.Random

fun main(args: Array<String>) {

   val rand = Random()
   while (true) {
       val a = rand.nextInt(20)
       println(a)
       if (a == 10) break
       println(rand.nextInt(20))
   }

}</lang>

Lang5

<lang lang5>do 20 ? int dup . 10 == if break then 20 ? int . loop</lang>

Lasso

<lang Lasso>local(x = 0) while(#x != 10) => {^ #x = integer_random(19,0) #x #x == 10 ? loop_abort ', '+integer_random(19,0)+'\r' ^}</lang>

LiveCode

<lang LiveCode>command loopForeverRandom

   repeat forever
       put random(20) - 1 into tRand
       put tRand
       if tRand is 10 then exit repeat
       put random(20) - 1
   end repeat

end loopForeverRandom </lang>

Liberty BASIC

The task specifies a "number". <lang lb>while num<>10

   num=rnd(1)*20
   print num
   if num=10 then exit while
   print rnd(1)*20

wend </lang>If "integer" was meant, this code fulfils that requirement. <lang lb>while num<>10

   num=int(rnd(1)*20)
   print num
   if num=10 then exit while
   print int(rnd(1)*20)

wend </lang>

Lisaac

<lang Lisaac>Section Header

+ name := TEST_LOOP_BREAK;

Section Public

- main <- (

 + a, b : INTEGER;

 `srand(time(NULL))`;
 {
   a := `rand()`:INTEGER % 20; // not exactly uniformly distributed, but doesn't matter
   a.print;
   '\n'.print;
   a == 10
 }.until_do {
   b := `rand()`:INTEGER % 20; // not exactly uniformly distributed, but doesn't matter
   b.print;
   '\n'.print;
 }

);</lang>

Lua

<lang lua>repeat

 k = math.random(19)
 print(k)
 if k == 10 then break end
 print(math.random(19)

until false</lang>

M4

<lang M4>define(`randSeed',141592653)dnl define(`setRand',

  `define(`randSeed',ifelse(eval($1<10000),1,`eval(20000-$1)',`$1'))')dnl

define(`rand_t',`eval(randSeed^(randSeed>>13))')dnl define(`random',

  `define(`randSeed',eval((rand_t^(rand_t<<18))&0x7fffffff))randSeed')dnl

dnl define(`loopbreak',`define(`a',eval(random%20))`a='a ifelse(a,10,`',`define(`b',eval(random%20))`b='b loopbreak')')dnl dnl loopbreak</lang>

Output:

a=17
b=3
a=0
b=15
a=10

Maple

<lang Maple>r := rand( 0 .. 19 ): do

       n := r();
       printf( "%d\n", n );
       if n = 10 then
               break
       end if;
       printf( "%d\n", r() );

end do:</lang>

Mathematica

<lang Mathematica>While[(Print[#];#!=10)&[RandomIntger[{0,19}]],

        Print[RandomInteger[{0,19}]
       ]</lang>

Maxima

<lang maxima>/* To exit the innermost block, use return(<value>) */

block([n],

  do (
     n: random(20),
     ldisp(n),
     if n = 10 then return(),
     n: random(20),
     ldisp(n)
  )

)$

/* To exit any level of block, use catch(...) and throw(<value>); they are not used for catching exceptions, but for non-local return. Use errcatch(...) for exceptions. */

block([n],

  catch(
     do (
        n: random(20),
        ldisp(n),
        if n = 10 then throw('done),
        n: random(20),
        ldisp(n)
     )
  )

)$

/* There is also break(<value>, ...) in Maxima. It makes Maxima stop the evaluation and enter a read-eval loop where one can change variable values, then return to the function after exit; For example */

block([x: 1], break(), ldisp(x)); > x: 2; > exit; 2</lang>

MAXScript

<lang MAXScript> while true do ( a = random 0 19 format ("A: % \n") a if a == 10 do exit b = random 0 19 format ("B: % \n") b ) </lang>

МК-61/52

Modula-3

<lang modula3>MODULE Break EXPORTS Main;

IMPORT IO, Fmt, Random;

VAR a,b: INTEGER;

BEGIN

 WITH rand = NEW(Random.Default).init() DO
   LOOP
     a := rand.integer(min := 0, max := 19);
     IO.Put(Fmt.Int(a) & "\n");
     IF a = 10 THEN EXIT END;
     b := rand.integer(min := 0, max := 19);
     IO.Put(Fmt.Int(b) & "\n");
   END;
 END;

END Break.</lang>

MOO

<lang moo>while (1)

 a = random(20) - 1;
 player:tell(a);
 if (a == 10)
   break;
 endif
 b = random(20) - 1;
 player:tell(b);

endwhile</lang>

MUMPS

<lang MUMPS>BREAKLOOP

NEW A,B
SET A=""
FOR  Q:A=10  DO
.SET A=$RANDOM(20)
.WRITE !,A
.Q:A=10
.SET B=$RANDOM(20)
.WRITE ?6,B
KILL A,B
QUIT
;A denser version that doesn't require two tests
NEW A,B 
FOR  SET A=$RANDOM(20) WRITE !,A QUIT:A=10  SET B=$RANDOM(20) WRITE ?6,B
KILL A,B QUIT</lang>

Output:

USER>D BREAKLOOP^ROSETTA
 
5     3
9     13
3     12
9     19
16    4
11    17
18    2
4     18
10
USER>D BREAKLOOP+11^ROSETTA
 
6     13
15    3
0     8
8     18
7     13
15    10
15    13
10

Nemerle

Translation of: C#

<lang Nemerle>using System; using System.Console; using Nemerle.Imperative;

module Break {

   Main() : void
   {
       def rnd = Random();
       while (true)
       {
           def a = rnd.Next(20);
           WriteLine(a);
           when (a == 10) break;
           def b = rnd.Next(20);
           WriteLine(b);
       }
   }

}</lang>

NetRexx

<lang NetRexx>/* NetRexx */ options replace format comments java crossref savelog symbols nobinary

 say
 say 'Loops/Break'
 rn = Rexx
 rnd = Random()

 loop label lb forever
   rn = rnd.nextInt(19)
   say rn.right(3)'\-'
   if rn = 10 then leave lb
   rn = rnd.nextInt(19)
   say rn.right(3)'\-'
   end lb
 say

</lang>

NewLISP

<lang NewLISP>(until (= 10 (println (rand 20)))

 (println (rand 20)))</lang>

Nim

Translation of: Python

<lang nim>import math

while true:

 let a = random(20)
 echo a
 if a == 10:
   break
 let b = random(20)
 echo b</lang>

Oberon-2

Works with oo2c Version 2 <lang oberon2> MODULE LoopBreak; IMPORT

 RandomNumbers,
 Out;

PROCEDURE Do(); VAR

 rn: LONGINT;

BEGIN

 LOOP
   rn := RandomNumbers.RND(20);
   Out.LongInt(rn,0);Out.Ln;
   IF rn = 10 THEN EXIT END;
   rn := RandomNumbers.RND(20);
   Out.LongInt(rn,0);Out.Ln
 END

END Do;

BEGIN

Do

END LoopBreak. </lang>

Objeck

<lang objeck> while(true) {

 a := (Float->Random() * 20.0)->As(Int);
 a->PrintLine();
 if(a = 10) { 
   break;
 };
 a := (Float->Random() * 20.0)->As(Int);
 a->PrintLine();

} </lang>

OCaml

<lang ocaml># Random.self_init();; - : unit = ()

while true do

   let a = Random.int 20 in
   print_int a;
   print_newline();
   if a = 10 then raise Exit;
   let b = Random.int 20 in
   print_int b;
   print_newline()
 done;;

15 18 2 13 10 Exception: Pervasives.Exit.</lang>

Octave

<lang octave>while(1)

 a = floor(unifrnd(0,20, 1));
 disp(a)
 if ( a == 10 )
   break
 endif
 b = floor(unifrnd(0,20, 1));
 disp(b)

endwhile</lang>

Oforth

<lang Oforth>while(true) [

     19 rand dup print ":" print
     10 == ifTrue: [ break ]
     19 rand print " " print
  ]</lang>

ooRexx

<lang ooRexx>/*REXX ****************************************************************

Three Ways to leave a Loop
ooRexx added the possibility to leave an outer loop
without using a control variable
12.05.2013 Walter Pachl
- - - - /

do i1=1 To 2 /* an outer loop */

 Say 'i1='i1                          /* tell where we are          */
 Call random ,,123                    /* seed to be reproducable    */
 do forever                           /* inner loop                 */
   a=random(19)
   Say a
   if a=6  then leave                 /* leaces the innermost loop  */
   end
 end

do i2=1 To 2

 Say 'i2='i2
 Call random ,,123
 do forever
   a=random(19)
   Say a
   if a=6  then leave i2    /* leaves loop with control variable i2 */
   end
 end

Parse Version v Select

 When pos('ooRexx',v)>0 Then supported=1
 Otherwise                   supported=0
 End

If supported Then Do

 Say 'Leave label-name is supported in' v

do Label i3 Forever

 Say 'outer loop'
 Call random ,,123
 do forever
   a=random(19)
   Say a
   if a=6  then leave i3          /* leaves loop with label name i3 */
   end
 end

End Else

 Say 'Leave label-name is probably not supported in' v</lang>

Output:

i1=1
14
14
5
6
i1=2
14
14
5
6
i2=1
14
14
5
6
Leave label-name is supported in REXX-ooRexx_4.1.2(MT) 6.03 28 Aug 2012
outer loop
14
14
5
6

Oz

We can implement this either with recursion or with a special type of the for-loop. Both can be considered idiomatic. <lang oz>for break:Break do

  R = {OS.rand} mod 20

in

  {Show R}
  if R == 10 then {Break}
  else {Show {OS.rand} mod 20}
  end

end</lang>

PARI/GP

<lang parigp>while(1,

 t=random(20);
 print(t);
 if(t==10, break);
 print(random(20))

)</lang>

Pascal

See Delphi

Perl

<lang perl>while (1) {

   my $a = int(rand(20));
   print "$a\n";
   if ($a == 10) {
       last;
   }
   my $b = int(rand(20));
   print "$b\n";

}</lang>

Perl 6

Works with: Rakudo version #21 "Seattle"

<lang perl6>loop {

   say my $n = (0..19).pick;
   last if $n == 10;
   say (0..19).pick;

}</lang>

Phix

Translation of: Euphoria

The rand() function returns a random integer from 1 to the integer provided. <lang Phix>integer i while 1 do

   i = rand(20)-1
   printf(1, "%g ", {i})
   if i=10 then exit end if
   printf(1, "%g\n", {rand(20)-1})

end while</lang>

Output:

PHP

<lang php>while (true) {

   $a = rand(0,19);
   echo "$a\n";
   if ($a == 10)
       break;
   $b = rand(0,19);
   echo "$b\n";

}</lang>

PicoLisp

Literally: <lang PicoLisp>(use R

  (loop
     (println (setq R (rand 1 19)))
     (T (= 10 R))
     (println (rand 1 19)) ) )</lang>

Shorter: <lang PicoLisp>(until (= 10 (println (rand 1 19)))

  (println (rand 1 19)) )</lang>

Pike

<lang pike>int main(){

  while(1){
     int a = random(20);
     write(a + "\n");
     if(a == 10){
        break;
     }
     int b = random(20);
     write(b + "\n");
  }

}</lang>

PL/I

<lang PL/I> do forever;

  k = trunc(random()*20);
  put (k);
  if k = 10 then leave;
  k = trunc(random()*20);
  put skip list (k);

end; </lang>

PostScript

<lang postscript>realtime srand % init RNG {

   rand 20 mod         % generate number between 0 and 19
   dup =               % print it
   10 eq { exit } if   % exit if 10

} loop</lang>

PowerShell

<lang powershell>$r = New-Object Random for () {

   $n = $r.Next(20)
   Write-Host $n
   if ($n -eq 10) {
       break
   }
   Write-Host $r.Next(20)

}</lang>

PureBasic

<lang PureBasic>If OpenConsole()

 Repeat
   a = Random(19)
   PrintN(Str(a))
   If a = 10
     Break
   EndIf 
   b = Random(19)
   PrintN(Str(b))
   PrintN("")
 ForEver

 Print(#CRLF$ + #CRLF$ + "Press ENTER to exit")
 Input()
 CloseConsole()

EndIf</lang>

Python

<lang python>import random

while True:

   a = random.randrange(20)
   print a
   if a == 10:
       break
   b = random.randrange(20)
   print b</lang>

R

Works with: R version 2.8.1

<lang R>sample0to19 <- function() sample(0L:19L, 1,replace=TRUE) repeat {

 result1 <- sample0to19()
 if (result1 == 10L)
 {
   print(result1)
   break
 }
 result2 <- sample0to19()
 cat(result1, result2, "\n")

}</lang>

Qi

<lang qi> (define loop -> (if (= 10 (PRINT (random 20)))

                   true
                   (do (PRINT (random 20))
                       (loop))))

(loop) </lang>

Racket

lang racket

(let loop ()

 (let/ec break
   (define a (random 20))
   (displayln a)
   (when (= a 10) (break))
   (displayln (random 20))
   (loop)))

</lang>

REBOL

<lang REBOL>REBOL [ Title: "Loop/Break" Author: oofoe Date: 2009-12-19 URL: http://rosettacode.org/wiki/Loop/Break ]

random/seed 1 ; Make repeatable.

random/seed now ; Uncomment for 'true' randomness.

r20: does [(random 20) - 1]

forever [ prin x: r20 if 10 = x [break] print rejoin [" " r20] ] print ""</lang>

Output:

Retro

<lang Retro>doc{ A couple of helper functions to make the rest of the code more readable. }doc

rand ( -n ) random 20 mod ;

. ( n- ) putn space ;

doc{ One approach is to use a simple repeat/again loop, and a conditional exit. For instance: }doc

foo ( - )

 repeat rand dup . 10 = if; rand . again ;

doc{ The other approach uses a structured while loop with the second printing handled by a conditional clause. }doc

[ rand dup . 10 <> [ [ rand . ] ifTrue ] sip ] while </lang>

REXX

<lang rexx>/*REXX program demonstrates a FOREVER DO loop with a test to LEAVE. */

     do forever                       /*perform until da cows come home*/
     a=random(19)                     /*same as:    random(0,19)       */
     call charout ,right(a,5)         /*show A right-justified, col. 1.*/
     if a==10  then leave             /*Random#=10? Then cows went home*/
     b=random(19)                     /*same as:    random(0,19)       */
     say right(b,5)                   /*show B right-justified, col. 2.*/
     end   /*forever*/
                                      /*stick a fork in it, we're done.*/</lang>

Output:

Ring

<lang ring> while true

     a = random(20)
     see a + nl
     if a = 10 exit ok

end </lang>

Ruby

<lang ruby>loop do

 a = rand(20)
 print a
 if a == 10
   puts
   break
 end
 b = rand(20)
 puts "\t#{b}"

end</lang> or <lang ruby>loop do

 print a = rand(20)
 puts or break if a == 10
 puts "\t#{rand(20)}"

end</lang>

Output:

Rust

<lang rust>// cargo-deps: rand

extern crate rand; use rand::distributions::{Range, IndependentSample};

fn main() {

   loop {
       let num = Range::new(0, 19 + 1).ind_sample(&mut rand::thread_rng());
       if num == 10 {
           println!("{}", num);
           break;
       }
   }

} </lang>

SAS

<lang sas>data _null_; do while(1);

  n=floor(uniform(0)*20);
  put n;
  if n=10 then leave;    /* 'leave' to break a loop */

end; run;</lang>

Sather

<lang sather>-- help class for random number sequence class RANDOM is

 attr seed:INT;

 create(seed:INT):SAME is
   res:RANDOM := new;
   res.seed := seed;
   return res;
 end;
 -- this code is taken from rand's man (C)
 next:INT is
   seed := seed * 1103515245 + 12345;
   return (seed/65536) % 32768;
 end;

end;

class MAIN is

 main is
   a, b :INT;
   rnd:RANDOM := #(1);
   loop
     a := rnd.next % 20;
     #OUT + a + "\n";
     if a = 10 then break!; end; -- here we break
     b := rnd.next % 20;
     #OUT + b + "\n";
   end; 
 end;

end;</lang>

Scala

<lang scala>scala> import util.control.Breaks.{breakable, break} import util.control.Breaks.{breakable, break}

scala> import util.Random import util.Random

scala> breakable {

    |   while(true) {
    |     val a = Random.nextInt(20)
    |     println(a)
    |     if(a == 10)
    |       break
    |     val b = Random.nextInt(20)
    |     println(b)
    |   }
    | }

5 4 10 </lang>

Scheme

<lang scheme> (let loop ((first (random 20)))

 (print first)
 (if (not (= first 10))
     (begin
       (print (random 20))
       (loop (random 20)))))

</lang>

Or by using call/cc to break out:

<lang scheme> (call/cc

(lambda (break)
  (let loop ((first (random 20)))
    (print first)
    (if (= first 10)
        (break))
    (print (random 20))
    (loop (random 20)))))

</lang>

Scilab

Works with: Scilab version 5.5.1

<lang>while %T

   a=int(rand()*20)  // [0..19] 
   printf("%2d ",a)
   if a==10 then break; end
   b=int(rand()*20)
   printf("%2d\n",b)

end printf("\n")</lang>

Output:

Sidef

<lang ruby>var lim = 20; loop {

   say (var n = lim.rand.int);
   n == 10 && break;
   say lim.rand.int;

}</lang>

Smalltalk

Works with: Smalltalk/X

<lang smalltalk>[

   |a b done|

   a := Random nextIntegerBetween:0 and:19.
   Stdout print: a; cr.
   (done := (a == 10)) ifFalse:[
       b := Random nextIntegerBetween:0 and:19.
       Stdout print:' '; print: b; cr.
   ].
   done

] whileFalse</lang>

alternative:

<lang smalltalk>[:exit |

   |first|

   Stdout printCR: (first := Random nextIntegerBetween:0 and:19).
   first == 10 ifTrue:[ exit value:nil ].
   Stdout print:' '; printCR: (Random nextIntegerBetween:0 and:19).

] loopWithExit.</lang>

SNOBOL4

Most Snobols lack a built-in rand( ) function. Kludgy "Linux-only" implementation: <lang snobol> input(.random,io_findunit(),1,"/dev/urandom") while &ALPHABET random @rand output = rand = rand - (rand / 20) * 20 eq(rand,10) :f(while) end</lang>

Or using a library function:

<lang SNOBOL4>* rand(n) -> real x | 0 <= x < n -include 'random.sno'

loop ne(output = convert(rand(20)'integer'),10) :s(loop) end</lang>

Suneido

<lang Suneido>forever

   {
   Print(i = Random(20))
   if i is 10
       break
   Print(i = Random(20))
   }

</lang>

Swift

<lang Swift>while true {

 let a = Int(arc4random()) % (20)
 print("a: \(a)",terminator: "   ")
 if (a == 10)
 {
   break
 }
 let b = Int(arc4random()) % (20)
 print("b: \(b)")

}

</lang>

Output:

a: 2   b: 7
a: 16   b: 13
a: 18   b: 16
a: 10

Tcl

<lang tcl>while true {

   set a [expr int(20*rand())]
   puts $a
   if {$a == 10} {
       break
   }
   set b [expr int(20*rand())]
   puts $b

}</lang>

TI-89 BASIC

<lang ti89b>Local x Loop

 rand(20)-1 → x
 Disp x                     © new line and text
 If x = 10 Then
   Exit
 EndIf
 Output 64, 50, rand(20)-1  © paint text to the right on same line

EndLoop</lang>

TorqueScript

<lang Torque>for(%a = 0; %a > -1; %a++) {

   %number = getRandom(0, 19);
   if(%number == 10)
       break;

}</lang>

TUSCRIPT

<lang tuscript> $$ MODE TUSCRIPT LOOP a=RANDOM_NUMBERS (0,19,1) IF (10==a) THEN

PRINT "a=",a
STOP

ELSE

b=RANDOM_NUMBERS (0,19,1)
PRINT "a=",a," b=",b

ENDIF IF (10==a,b) STOP ENDLOOP </lang>

Output:

a=0 b=17
a=11 b=13
a=3 b=16
a=17 b=13
a=8 b=11
a=8 b=0
a=6 b=2
a=10

UNIX Shell

This script gets random numbers from jot(1). If there is any error with jot(1), the script exits.

Works with: Bourne Shell

Library: jot

<lang bash>while true; do a=`jot -w %d -r 1 0 20` || exit $? echo $a test 10 -eq $a && break b=`jot -w %d -r 1 0 20` || exit $? echo $b done</lang>

Korn Shells have a RANDOM parameter.

Works with: Bash

Works with: pdksh version 5.2.14

<lang bash>while true; do

 echo $((a=RANDOM%20))
 [ $a -eq 10 ] && break
 echo $((b=RANDOM%20))

done</lang>

Ursa

Translation of: Python

<lang ursa>decl ursa.util.random r decl int a b while true

       set a (r.getint 19)
       out a endl console
       if (= a 10)
               break
       end while
       set b (r.getint 19)
       out b endl console

end while</lang>

VBScript

Implementation

Based on BASIC version. Demonstrates breaking out of do/loop and for/next (Exit is good for getting out of functions and subs as well)

<lang vb> do a = int( rnd * 20) wscript.stdout.write a if a = 10 then exit do b = int( rnd * 20 ) wscript.echo vbnullstring,b loop

dim i for i = 1 to 100000 a = int( rnd * 20) wscript.stdout.write a if a = 10 then exit for b = int( rnd * 20 ) wscript.echo vbnullstring,b next </lang>

XPL0

<lang XPL0>include c:\cxpl\codes; int N; loop [N:= Ran(20);

       IntOut(0, N);
       if N=10 then quit;
       ChOut(0, 9\tab\);
       IntOut(0, Ran(20));
       CrLf(0);
       ]</lang>

Output:

zkl

<lang zkl>while(1){n:=(0).random(20); n.print(" ");

  if (n==10){ println(); break; } (0).random().println();

}</lang>

Output:

7  2139341079
4  3217334923
18  2050357211
2  2061361000
10