Loops/Break

Loops/Break
You are encouraged to solve this task according to the task description, using any language you may know.

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.

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 1..20;
  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>

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>

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>

C

<lang c>#include <stdlib.h>

1. include <time.h>
2. include <stdio.h>

int main() {

   int a, b;

   srand(time(NULL));
   while (1) {
       a = rand() % 20; /* not exactly uniformly distributed, but doesn't matter */
       printf("%d\n", a);
       if (a == 10) break;
       b = rand() % 20; /* not exactly uniformly distributed, but doesn't matter */
       printf("%d\n", b);
   }
   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>

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>

Common Lisp

<lang lisp>(loop

   (setq a (random 20))
   (print a)
   (if (= a 10)
       (return))
   (setq b (random 20))
   (print b))</lang>

D

Works with: Tango

Using Mersenne twister;

<lang D>import tango.io.Stdout; import tango.math.random.Twister;

void main() {

   alias Twister.instance r;
   uint x;

   while (~1) {
       x = r.natural(20);
       Stdout (x) (" ");
       if (x == 10) break;
       Stdout (r.natural(20)).newline;
   }

}</lang>

E

<lang e>while (true) {

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

}</lang>

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 20 random . ] loop</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>

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

<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>

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.

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

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>

OCaml

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

1. 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>

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>

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 {

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

}</lang>

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>

PL/I

<lang PL/I> do forever;

  k = random()*19;
  put (k);
  if k = 10 then leave;
  k = random()*19;
  put skip list (k);

end; </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>

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>

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:

14 11
19 15
6 11
12 11
3 14
10

REXX

<lang rexx>do forever

 a = random(19)
 say a
 if a = 10 then leave
 b = random(19)
 say b

end</lang>

Ruby

<lang ruby>loop do

   a = rand(20)
   puts a
   if a == 10
       break
   end
   b = rand(20)
   puts b

end</lang>

Scala

Works with: Scala version 2.7

A break library method is available in Scala 2.8 but not 2.7

<lang Scala> import scala.util.Random

val rand = new Random var doNext = true

while(doNext) {

 val first = rand.nextInt(20)
 println(first)

 if (first != 10) {
   val second = rand.nextInt(20)
   println(second)
 } else {
   doNext = false
 }

} </lang>

SNOBOL4

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>

Suneido

<lang Suneido>forever

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

</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>

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>

Unicon

See Icon.

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>