Loops/While: Difference between revisions

Content added Content deleted

Inline

Revision as of 00:18, 30 March 2013

Start an integer value at 1024. Loop while it is greater than 0. Print the value (with a newline) and divide it by two each time through the loop.

6502 Assembly

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

LDA #$00 ;the 6502 is an 8-bit processor STA Ilow ;and so 1024 ($0400) must be stored in two memory locations LDA #$04 STA Ihigh WhileLoop: LDA Ilow BNE NotZero LDA Ihigh BEQ EndLoop NotZero: JSR PrintI ;routine not implemented LSR Ihigh ;shift right ROR Ilow ;rotate right JMP WhileLoop

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

ActionScript

<lang actionscript>var i:int = 1024; while (i > 0) {

   trace(i);
   i /= 2;

}</lang>

Ada

<lang ada>declare

  I : Integer := 1024;

begin

  while I > 0 loop
     Put_Line(Integer'Image(I));
     I := I / 2;
  end loop;

end;</lang>

ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8-8d

<lang algol68>INT i := 1024; WHILE i > 0 DO

  print(i);
  i := i OVER 2

OD</lang> Output:

      +1024       +512       +256       +128        +64        +32        +16         +8         +4         +2         +1

AmbientTalk

Note: in AmbientTalk, while:do: is a keyworded message (as in Smalltalk). Both arguments to this message must be blocks (aka anonymous functions or thunks).

<lang ambienttalk> // print 1024 512 etc def i := 1024; while: { i > 0 } do: {

 system.print(" "+i);
 i := i/2;

} </lang>

AmigaE

<lang amigae>PROC main()

 DEF i = 1024
 WHILE i > 0
   WriteF('\d\n', i)
   i := i / 2
 ENDWHILE

ENDPROC</lang>

AppleScript

AppleScript does not natively support a standard out. Use the Script Editor's Event Log as the output. <lang AppleScript >set i to 1024 repeat while i > 0 log i set i to i / 2 end repeat</lang>

Applesoft BASIC

10 I% = 1024
20  IF I% > 0 THEN  PRINT I%:I% = I% / 2: GOTO 20

</lang>

AutoHotkey

<lang AutoHotkey>i = 1024 While (i > 0) {

 output = %output%`n%i%
 i := Floor(i / 2)

} MsgBox % output</lang>

AWK

<lang awk>BEGIN {

 v = 1024
 while(v > 0) {
   print v
   v = int(v/2)
 }

}</lang>

BASIC

Works with: QuickBasic version 4.5

<lang qbasic>i = 1024 while i > 0

  print i
  i = i / 2

wend</lang>

BBC BASIC

Works with: BBC BASIC for Windows

<lang bbcbasic> i% = 1024

     WHILE i%
       PRINT i%
       i% DIV= 2
     ENDWHILE</lang>

Befunge

<lang befunge>84*:*> :v

    ^/2.:_@</lang>

Brat

Converts to integers so output is a little bit shorter and neater.

<lang brat>i = 1024 while { i > 0 } {

   p i
   i = (i / 2).to_i

}</lang>

C

<lang c>int i = 1024; while(i > 0) {

 printf("%d\n", i);
 i /= 2;

}</lang> In for loop fashion: <lang c>int i; for(i = 1024;i > 0; i/=2){

  printf("%d\n", i);

}</lang>

C++

<lang cpp>int i = 1024; while(i > 0) {

 std::cout << i << std::endl;
 i /= 2;

}</lang> Alternatively, it can be done with for: <lang cpp>for (int i = 1024; i>0; i /= 2)

 std::cout << i << std::endl;</lang>

Indeed, in C++, <lang cpp>for (init; cond; update)

 statement;</lang>

is equivalent to <lang cpp>{

 init;
 while (cond)
 {
   statement;
   update;
 }

}</lang>

C#

<lang csharp>int i = 1024; while(i > 0){

  System.Console.WriteLine(i);
  i /= 2;

}</lang>

Clojure

<lang lisp>(def i (ref 1024))

(while (> @i 0)

 (println @i)
 (dosync (ref-set i (quot @i 2))))</lang>

2 ways without mutability:

<lang Clojure>(loop [i 1024]

 (when (pos? i)
   (println i)
   (recur (quot i 2))))

(doseq [i (take-while pos? (iterate #(quot % 2) 1024))]

 (println i))</lang>

ColdFusion

Remove the leading space from the line break tag.

With tags: <lang cfm><cfset i = 1024 /> <cfloop condition="i GT 0">

 #i#< br />
 <cfset i /= 2 />

</cfloop></lang> With script: <lang cfm><cfscript>

 i = 1024;
 while( i > 0 )
 {
   writeOutput( i + "< br/ >" );
 }

</cfscript></lang>

Common Lisp

<lang lisp>(setq i 1024) (loop while (> i 0) do

 (print i)
 (setq i (floor i 2)))</lang>

Creative Basic

DEF X:INT

X=1024

OPENCONSOLE

WHILE X>0

  X=X/2
  PRINT X

ENDWHILE

'Keep console from closing right away so the figures can be read. WHILE INKEY$="":ENDWHILE

CLOSECONSOLE

'Since this is, in fact, a Creative Basic console program. END

'Note: Spacing is not an issue. I just find the code to be more readable with spaces. </lang>

Crack

<lang crack>i = 1024; while( i > 0 ) {

 cout ` $i\n`;
 i = i/2;

} </lang>

D

<lang d>import std.stdio;

void main() {

   int i = 1024;

   while (i > 0) {
       writeln(i);
       i >>= 1;
   }

}</lang>

Output:

Dc

People may think all loops in Dc looks alike. In fact, there aren't loop, but conditional execution in Dc. You expand and execute the content of a register (in here, p) whenever the condition is satisfied. <lang Dc>1024[p2/d0<p]dspx</lang>

Dao

<lang dao>i = 1024; while( i > 0 ) i = i / 2; </lang>

Delphi

<lang Delphi>var

 i : Integer;

begin

 i := 1024;

 while i > 0 do
 begin
   Writeln(i);
   i := i div 2;
 end;

end;</lang>

DWScript

<lang Delphi>var i := 1024;

while i > 0 do begin

  PrintLn(i);
  i := i div 2;

end;</lang>

E

<lang e>var i := 1024 while (i > 0) {

   println(i)
   i //= 2

}</lang>

EGL

<lang EGL>x int = 1024; while ( x > 0 )

  SysLib.writeStdout( x );
  x = MathLib.floor( x / 2 );

end</lang>

Euphoria

<lang Euphoria> integer i i = 1024

while i > 0 do

   printf(1, "%g\n", {i})
   i = floor(i/2) --Euphoria does NOT use integer division.  1/2 = 0.5

end while </lang> Even without the floor() the code will in fact end. But it's FAR beyond 1.

Factor

<lang factor>1024 [ dup 0 > ] [ dup . 2 /i ] while drop</lang>

FALSE

Fantom

<lang fantom> class Main {

 public static Void main ()
 {
   Int i := 1024
   while (i > 0)
   {
     echo (i)
     i /= 2
   }
 }

} </lang>

Forth

<lang forth>: halving ( n -- )

 begin  dup 0 >
 while  cr dup .  2/
 repeat drop ;

1024 halving</lang>

Fortran

Works with: Fortran version 90 and later

<lang fortran>INTEGER :: i = 1024 DO WHILE (i > 0)

 WRITE(*,*) i
 i = i / 2

END DO</lang>

Works with: Fortran version 77 and later

<lang fortran> PROGRAM LOOPWHILE

       INTEGER I

C FORTRAN 77 does not have a while loop, so we use GOTO statements C with conditions instead. This is one of two easy ways to do it.

       I = 1024
  10   CONTINUE

C Check condition.

       IF (I .GT. 0) THEN

C Handle I.

         WRITE (*,*) I
         I = I / 2

C Jump back to before the IF block.

         GOTO 10
       ENDIF

C This is an alternative while loop with labels on both ends. This C will use the condition as a break rather than create an entire C IF block. Which you use is up to you, but be aware that you must C use this one if you plan on allowing for breaks.

       I = 1024
  20   CONTINUE

C If condition is false, break.

         IF (I .LE. 0) GOTO 30

C Handle I.

         WRITE (*,*) I
         I = I / 2

C Jump back to the "loop" beginning.

         GOTO 20
  30   CONTINUE

       STOP
     END</lang>

Frink

<lang frink> i=1024 while i>0 {

  i = i/1

} </lang>

GML

<lang GML>i = 1024 while(i > 0)

   {
   show_message(string(i))
   i /= 2
   }</lang>

Go

<lang go>i := 1024 for i > 0 {

 fmt.Printf("%d\n", i)
 i /= 2

}</lang>

Groovy

Solution: <lang groovy>int i = 1024 while (i > 0) {

   println i
   i /= 2

}</lang>

Output:

Haskell

<lang haskell>import Control.Monad (when) main = loop 1024

 where loop n = when (n > 0)
                     (do print n
                         loop (n `div` 2))</lang>

You could try to write a "while" that operates on monads:

<lang haskell>import Control.Monad (when)

whileM :: (Monad m) => m Bool -> m a -> m () whileM cond body = do c <- cond

                     when c (body >> whileM cond body)</lang>

You can use it like this

<lang haskell>import Data.IORef

main :: IO () main = do r <- newIORef 1024

         whileM (do n <- readIORef r
                    return (n > 0))
                (do n <- readIORef r
                    print n
                    modifyIORef r (`div` 2))</lang>

Icon and Unicon

<lang icon>procedure main()

  local i
  i := 1024
  while write(0 < (i := i / 2))

end</lang>

Inform 7

<lang inform7>let N be 1024; while N > 0: say "[N][line break]"; let N be N / 2;</lang>

IWBASIC

DEF X:INT

X=1024

OPENCONSOLE

WHILE X>0

   X=X/2
   PRINT X

ENDWHILE

'Keep the console from closing right away so the figures can be read. WHILE INKEY$="":ENDWHILE

CLOSECONSOLE

'Note: Spacing is not an issue. I just find the code to be more readable with spaces. </lang>

J

J is array-oriented, so there is very little need for loops. For example, one could satisfy this task this way:

J does support loops for those times they can't be avoided (just like many languages support gotos for those time they can't be avoided).

<lang j>monad define 1024

 while. 0 < y do.
   smoutput y
   y =. <. -: y 
 end.
 i.0 0

)</lang>

Note: this defines an anonymous function (monad define, and the subsequent lines) and passes it the argument 1024, which means it will be executed as soon as the full definition is available.

Java

<lang java5>int i = 1024; while(i > 0){

  System.out.println(i);
  i >>= 1; //also acceptable: i /= 2;

}</lang> With a for loop: <lang java5>for(int i = 1024; i > 0;i /= 2 /*or i>>= 1*/){

  System.out.println(i);

}</lang>

JavaScript

<lang javascript>var n = 1024; while (n>0) {

print(n);
n/=2;

}</lang>

Joy

<lang joy>DEFINE putln == put '\n putch.

1024 [] [dup putln 2 /] while.</lang>

LabVIEW

Use Round Towards -Inf to prevent the integer becoming a float.
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.

Lang5

Translation of: Factor

<lang lang5>: /i / int ; : 0= 0 == ;

dip swap '_ set execute _ ; : dupd 'dup dip ;

2dip swap '_x set swap '_y set execute _y _x ;

while

   do  dupd 'execute 2dip
       rot 0= if break else dup 2dip then
   loop ;

1024 "dup 0 >" "dup . 2 /i" while</lang>

Liberty BASIC

All integers are changed to floats if an operation creates a non-integer result. Without using int() the program keeps going until erroring because accuracy was lost. <lang lb> i = 1024 while i > 0

  print i
  i = int( i / 2)

wend end </lang>

Lisaac

<lang Lisaac>+ i : INTEGER; i := 1024; { i > 0 }.while_do {

 i.println;
 
 i := i / 2;

};</lang>

Logo

<lang logo>make "n 1024 while [:n > 0] [print :n make "n :n / 2]</lang>

Lua

<lang lua> n = 1024 while n>0 do

 print(n)
 n = math.floor(n/2)

end </lang>

Maple

To avoid generating an infinite sequence (1/2, 1/4, 1/8, 1/16, etc.) of fractions after n takes the value 1, we use integer division (iquo) rather than the solidus operation (/). <lang Maple> > n := 1024: while n > 0 do print(n); n := iquo(n,2) end:

</lang>

Mathematica

Mathematica does not support integer-rounding, it would result in getting fractions: 1/2, 1/4 , 1/8 and so on; the loop would take infinite time without using the Floor function: <lang Mathematica>i = 1024; While[i > 0,

Print[i];
i = Floor[i/2];

]</lang>

MATLAB / Octave

In Matlab (like Octave) the math is done floating point, then rounding to integer, so that 1/2 will be always 1 and never 0. A 'floor' is used to round the number. <lang Matlab>i = 1024; while (i > 0)

   disp(i);
   i = floor(i/2);

end</lang>

A vectorized version of the code is

<lang Matlab> printf('%d\n', 2.^[log2(1024):-1:0]); </lang>

Maxima

<lang maxima>block([n], n: 1024, while n > 0 do (print(n), n: quotient(n, 2)));

/* using a C-like loop: divide control variable by two instead of incrementing it */ for n: 1024 next quotient(n, 2) while n > 0 do print(n);</lang>

MAXScript

<lang maxscript>a = 1024 while a > 0 do (

   print a
   a /= 2

)</lang>

Make

<lang make>NEXT=`expr $* / 2` MAX=10

all: $(MAX)-n;

0-n:;

%-n: %-echo

      @-make -f while.mk $(NEXT)-n MAX=$(MAX)

%-echo:

      @echo $*</lang>

Invoking it <lang make>|make -f while.mk MAX=1024</lang>

Metafont

Metafont has no while loop, but it can be "simulated" easily.

<lang metafont>a := 1024; forever: exitif not (a > 0);

 show a;
 a := a div 2;

endfor</lang>

MIRC Scripting Language

<lang mirc>alias while_loop {

 var %n = 10
 while (%n >= 0) {
   echo -a Countdown: %n
   dec %n
 }

}</lang>

МК-61/52

Modula-2

<lang modula2>MODULE DivBy2;

 IMPORT InOut;

 VAR
   i: INTEGER;

BEGIN

 i := 1024;
 WHILE i > 0 DO
   InOut.WriteInt(i, 4);
   InOut.WriteLn;
   i := i DIV 2
 END

END DivBy2.</lang>

Modula-3

The usual module code and imports are omitted. <lang modula3>PROCEDURE DivBy2() =

 VAR i: INTEGER := 1024;
 BEGIN
   WHILE i > 0 DO
     IO.PutInt(i);
     IO.Put("\n");
     i := i DIV 2;
   END;
 END DivBy2;</lang>

MOO

<lang moo>i = 1024; while (i > 0)

 player:tell(i);
 i /= 2;

endwhile</lang>

NetRexx

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

 say
 say 'Loops/While'

 x_ = 1024
 loop while x_ > 0
   say x_.right(6)
   x_ = x_ % 2 -- integer division
   end

</lang>

Nimrod

<lang python>var n: int = 1024 while n > 0:

 echo(n)
 n = n div 2</lang>

Nemerle

<lang Nemerle>mutable x = 1024; while (x > 0) {

   WriteLine($"$x");
   x /= 2;

}</lang> Or, with immutable types, after Haskell: <lang Nemerle> // within another function, eg Main() def loop(n : int) : void {

   when (n > 0)
   {
       WriteLine($"$n");
       loop(n / 2);
   }

}

loop(1024)</lang>

Oberon-2

The usual module code and imports are ommited. <lang oberon2>PROCEDURE DivBy2*();

 VAR i: INTEGER;

BEGIN

 i := 1024;
 WHILE i > 0 DO
   Out.Int(i,0);
   Out.Ln;
   i := i DIV 2;
 END;

END DivBy2;</lang>

Objeck

<lang objeck> i := 1024; while(i > 0) {

  i->PrintLine();
  i /= 2;

}; </lang>

OCaml

<lang ocaml>let n = ref 1024;; while !n > 0 do

 Printf.printf "%d\n" !n;
 n := !n / 2

done;;</lang>

But it is more common to write it in a tail-recursive functional style: <lang ocaml>let rec loop n =

 if n > 0 then begin
   Printf.printf "%d\n" n;
   loop (n / 2)
 end

in loop 1024</lang>

Octave

<lang octave>i = 1024; while (i > 0)

 disp(i)
 i = floor(i/2);

endwhile</lang>

The usage of the type int32 is not convenient, since the math is done floating point, then rounding to integer, so that 1/2 will be always 1 and never 0.

Oz

Oz' for-loop can be used in a C-like manner: <lang oz>for I in 1024; I>0; I div 2 do

  {Show I}

end</lang>

Alternatively, we can use the while feature of the for-loop with a mutable variable: <lang oz>declare

 I = {NewCell 1024}

in

 for while:@I > 0 do
    {Show @I}
    I := @I div 2
 end</lang>

PARI/GP

<lang parigp>n=1024; while(n,

 print(n);
 n/=2

);</lang>

Pascal

<lang pascal>program divby2(output);

var

 i: integer;

begin

 i := 1024;
 while i > 0 do
   begin
     writeln(i);
     i := i div 2
   end

end.</lang>

Perl

<lang perl>my $n = 1024; while ($n) {

   print "$n\n";
   $n = int $n / 2;

}</lang>

until (condition) is equivalent to while (not condition).

<lang perl>my $n = 1024; until ($n <= 0) {

   print "$n\n";
   $n = int $n / 2;

}</lang>

Perl 6

Here is a straightforward translation of the task description: <lang perl6>my $n = 1024; while $n > 0 { say $n; $n div= 2 }</lang>

The same thing with a C-style loop and a bitwise shift operator: <lang perl6>loop (my $n = 1024; $n > 0; $n +>= 1) { say $n }</lang>

And here's how you'd really write it, using a sequence operator that intuits the division for you:

PHP

<lang php>$i = 1024; while ($i > 0) {

  echo "$i\n";
  $i >>= 1;

}</lang>

PicoLisp

<lang PicoLisp>(let N 1024

  (while (gt0 N)
     (println N)
     (setq N (/ N 2)) ) )</lang>

Pike

<lang pike>int main(){

  int i = 1024;
  while(i > 0){
     write(i + "\n");
     i = i / 2;
  }

}</lang>

PL/I

<lang PL/I> declare i fixed binary initial (1024);

do while (i>0);

  put skip list (i);
  i = i / 2;

end; </lang>

Pop11

<lang pop11>lvars i = 1024; while i > 0 do

   printf(i, '%p\n');
   i div 2 -> i;

endwhile;</lang>

PostScript

PostScript has no real while loop, but it can easily be created with an endless loop and a check at the beginning: <lang postscript>1024 {

   dup 0 le     % check whether still greater than 0
   { pop exit } % if not, exit the loop
   if
   dup =        % print the number
   2 idiv       % divide by two

} loop</lang>

PowerShell

<lang powershell>[int]$i = 1024 while ($i -gt 0) {

   $i
   $i /= 2

}</lang>

Prolog

<lang prolog>while(0) :- !. while(X) :- X>0,write(X), nl, X1 is X // 2, while(X1).</lang>

PureBasic

<lang PureBasic>If OpenConsole()

 x.i = 1024
 While x > 0
   PrintN(Str(x))
   x / 2
 Wend

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

EndIf</lang>

Python

<lang python>n = 1024 while n > 0:

   print n
   n //= 2</lang>

R

<lang R>i <- 1024L while(i > 0) {

  print(i)
  i <- i %/% 2

}</lang>

REBOL

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

value: 1024 while [value > 0][ print value value: to-integer value / 2 ]</lang>

Racket

lang racket

(let loop ([n 1024])

 (when (positive? n)
   (displayln n)
   (loop (quotient n 2))))

</lang>

Retro

<lang Retro>1024 [ cr &putn sip 2 / dup ] while</lang>

REXX

version 1

<lang rexx>/*REXX program to show a DO WHILE construct. */ j=1024

        do while j>0
        say j
        j=j%2                /*in REXX, %  is integer division. */
        end</lang>

output

version 2, right justified

Note that a faster version could be implemented with
DO WHILE x\==0
but that isn't compliant with the wording of the task. <lang rexx>/*REXX program to show a DO WHILE construct. */ x=1024

        do while x>0
        say right(x,10)      /*pretty up the output by aligning.*/
        x=x%2                /*in REXX, %  is integer division. */
        end</lang>

output

version 3, faster WHILE comparison

<lang rexx>/*REXX program to show a DO WHILE construct. */ x=1024

        do while x>>0        /*this is an exact comparison.     */
        say right(x,10)      /*pretty up the output by aligning.*/
        x=x%2                /*in REXX, %  is integer division. */
        end</lang>

output is the same as version 2.

Ruby

<lang ruby>i = 1024 while i > 0 do

  puts i
  i /= 2

end</lang> The above can be written in one statement (using the return value of the Kernel#puts method: nil is false), but the readability suffers: <lang ruby>i = 1024 puts i or i /= 2 while i > 0</lang>

until condition is equivalent to while not condition.

<lang ruby>i = 1024 until i <= 0 do

  puts i
  i /= 2

end</lang>

Run BASIC

<lang runbasic>i = 1024 while i > 0

  print i
  i = int(i / 2)

wend end</lang>

SAS

<lang sas>data _null_; n=1024; do while(n>0);

 put n;
 n=int(n/2);

end; run;</lang>

Sather

<lang sather>class MAIN is

 main is
   i ::= 1024;
   loop while!(i > 0);
     #OUT + i + "\n";
     i := i / 2;
   end;
 end;

end;</lang>

Scala

<lang scala>var i = 1024 while (i > 0) {

 println(i)
 i /= 2

}</lang>

Scheme

<lang scheme>(do ((n 1024 (quotient n 2)))

   ((<= n 0))
   (display n)
   (newline))</lang>

Seed7

<lang seed7>$ include "seed7_05.s7i";

const proc: main is func

 local
   var integer: i is 1024;
 begin
   while i > 0 do
     writeln(i);
     i := i div 2
   end while;
 end func;</lang>

Slate

n := 1024.

[n isPositive] whileTrue:

 [inform: number printString.
  n := n // 2]

</lang>

Smalltalk

<lang smalltalk>number := 1024. [ number > 0 ] whileTrue:

 [ Transcript print: number; nl.
 number := number // 2 ]</lang>

<lang smalltalk>number := 1024. [ number <= 0 ] whileFalse:

 [ Transcript print: number; nl.
 number := number // 2 ]</lang>

Standard ML

<lang sml>val n = ref 1024; while !n > 0 do (

 print (Int.toString (!n) ^ "\n");
 n := !n div 2

)</lang>

But it is more common to write it in a tail-recursive functional style: <lang sml>let

 fun loop n =
   if n > 0 then (
     print (Int.toString n ^ "\n");
     loop (n div 2)
   ) else ()

in

 loop 1024

end</lang>

Suneido

<lang Suneido>i = 1024 while (i > 0)

   {
   Print(i)
   i = (i / 2).Floor()
   }</lang>

Output: <lang Suneido>1024 512 256 128 64 32 16 8 4 2 1</lang>

Tcl

<lang tcl>set i 1024 while {$i > 0} {

   puts $i
   set i [expr {$i / 2}]

}</lang>

TI-89 BASIC

<lang ti89b>Local i 1024 → i While i > 0

 Disp i
 intDiv(i, 2) → i

EndWhile</lang>

TorqueScript

This has to make use of mFloor because torque has automatic type shuffling, causing an infiniteloop. <lang Torque>%num = 1024; while(%num > 0) {

   echo(%num);
   %num = mFloor(%num / 2);

}</lang>

Trith

<lang trith>1024 [dup print 2 / floor] [dup 0 >] while drop</lang> <lang trith>1024 [dup print 1 shr] [dup 0 >] while drop</lang>

TUSCRIPT

<lang tuscript> $$ MODE TUSCRIPT i=1024 LOOP

  PRINT i
  i=i/2
  IF (i==0) EXIT

ENDLOOP </lang> Output:

Unicon

See Icon.

UNIX Shell

Works with: Bourne Again SHell

<lang bash>x=1024 while $x -gt 0 ; do

 echo $x
 x=$(( $x/2 ))

done</lang>

UnixPipes

<lang bash>(echo 1024>p.res;tail -f p.res) | while read a ; do

  test $a -gt 0 && (expr $a / 2  >> p.res ; echo $a) || exit 0

done</lang>

Ursala

Unbounded iteration is expressed with the -> operator. An expression (p-> f) x, where p is a predicate and f is a function, evaluates to x, f(x), or f(f(x)), etc. as far as necessary to falsify p.

Printing an intermediate result on each iteration is a bigger problem because side effects are awkward. Instead, the function g in this example iteratively constructs a list of results, which is displayed on termination.

The argument to g is the unit list <1024>. The predicate p is ~&h, the function that tests whether the head of a list is non-null (equivalent to non-zero). The iterated function f is that which conses the truncated half of the head of its argument with a copy of the whole argument. The main program takes care of list reversal and formatting. <lang Ursala>#import nat

g = ~&h-> ^C/half@h ~&

show+

main = %nP*=tx g <1024></lang> output:

Explicit iteration has its uses but there are always alternatives. The same output is produced by the following main program using bit manipulation. <lang Ursala>main = %nP*=tK33 1024</lang>

V

<lang v>1024 [0 >] [

  dup puts
  2 / >int

] while</lang>

Vedit macro language

<lang vedit>#1 = 1024 while (#1 > 0) {

   Num_Type(#1)
   #1 /= 2

}</lang> or with for loop: <lang vedit>for (#1 = 1024; #1 > 0; #1 /= 2) {

   Num_Type(#1)

}</lang>

Visual Basic .NET

<lang vbnet>Dim x = 1024 Do

   Console.WriteLine(x)
   x = x \ 2

Loop While x > 0</lang>

XPL0

<lang XPL0>code CrLf=9, IntOut=11; int I; [I:= 1024; while I>0 do

       [IntOut(0, I);  CrLf(0);
       I:= I>>1;       \(same as I/2 for positive I)
       ];

]</lang>