Loop/While

From Rosetta Code

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.

Contents 1 Ada 2 BASIC 3 Befunge 4 C 5 ColdFusion 6 D 7 Forth 8 Factor 9 Fortran 10 Haskell 11 J 12 Java 13 JavaScript 14 Logo 15 MAXScript 16 Make 17 Oberon-2 18 OCaml 19 Pascal 20 Perl 21 Pop11 22 Python 23 Scheme 24 UnixPipes 25 V

[edit] Ada

 
declare
   I : Integer := 1024;
begin
   while I > 0 loop
      Put_Line(Integer'Image(I));
      I := I / 2;
   end loop;
end;
 

[edit] BASIC

Works with: QuickBasic version 4.5

i = 1024
WHILE i > 0
   PRINT i
   i = i / 2
WEND

[edit] Befunge

84*:*>   :v
     ^/2.:_@

[edit] C

int i = 1024;
while(i > 0) {
  printf("%d\n", i);
  i /= 2;
}

[edit] ColdFusion

Remove the leading space from the line break tag.

With tags:

<cfset i = 1024 />
<cfloop condition="i GT 0">
  #i#< br />
  <cfset i /= 2 />
</cfloop>

With script:

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

[edit] D

import std.stdio;
 
int i = 1024;
void main() {
    while(i > 0) {
        writefln("%s", i);
        i >>= 1;
    }
}

[edit] Forth

: halving ( n -- )
  begin  dup 0 >
  while  cr dup .  2/
  repeat drop ;
1024 halving

[edit] Factor

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

[edit] Fortran

Works with: Fortran version 90 and later

INTEGER :: i = 1024
DO WHILE (i > 0)
  WRITE(*,*) i
  i = i / 2
END DO

[edit] Haskell

import Control.Monad
main = loop 1024      
  where loop n = when (n > 0)
                      (do print n
                          loop (n `div` 2))

[edit] J

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

  ,. <.@-:^:*^:a: 1024

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).

  3 : 0 ] 1024

       while. 0 < y do.
            y 1!:2 ] 2
            y =. <. -: y 
       end.

      i. 0 0
  )

Though it's rare to see J code like this.

[edit] Java

int i = 1024;
while(i > 0){
   System.out.println(i);
   i >>= 1; //also acceptable: i /= 2;
}

[edit] JavaScript

var n = 1024;
while (n>0) {
 print(n);
 n/=2;
}

[edit] Logo

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

[edit] MAXScript

a = 1024
while a > 0 do
(
    print a
    a /= 2
)

[edit] Make

NEXT=`expr $* / 2`
MAX=10

all: $(MAX)-n;

0-n:;

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

%-echo:
       @echo $*

Invoking it

|make -f while.mk MAX=1024

[edit] Oberon-2

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;

[edit] OCaml

let n = ref 1024;;
while !n > 0 do
  Printf.printf "%d\n" !n;
  n := !n / 2
done;;

But it is more common to write it in a tail-recursive functional style:

let rec loop n =
  if n > 0 then begin
    Printf.printf "%d\n" n;
    loop (n / 2)
  end
in loop 1024

[edit] Pascal

 
program divby2(output);
 
var
  i: integer;
 
begin
  i := 1024;
  while i > 0 do
    begin
      writeln(i);
      i := i div 2
    end
end.
 

[edit] Perl

$n = 1024;
while ($n > 0) {
    print "$n\n";
    $n >>= 1; # also acceptable: use integer; $n /= 2;
}

[edit] Pop11

lvars i = 1024;
while i > 0 do
    printf(i, '%p\n');
    i div 2 -> i;
endwhile;

[edit] Python

n = 1024
while n > 0:
    print n
    n = n / 2

[edit] Scheme

 
(do ((n 1024 (quotient n 2)))
    ((<= n 0))
    (display n)
    (newline))

[edit] UnixPipes

(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

[edit] V

1024 [0 >] [
   dup puts
   2 / >int
] while