Loops/While
From Rosetta Code
[edit] ActionScript
var i:int = 1024;
while (i > 0) {
trace(i);
i /= 2;
}
[edit] Ada
declare
I : Integer := 1024;
begin
while I > 0 loop
Put_Line(Integer'Image(I));
I := I / 2;
end loop;
end;
[edit] ALGOL 68
Works with: ALGOL 68 version Standard - no extensions to language used Works with: ALGOL 68G version Any - tested with release mk15-0.8b.fc9.i386 Works with: ELLA ALGOL 68 version Any (with appropriate job cards) - tested with release 1.8.8d.fc9.i386
INT i := 1024;
WHILE i > 0 DO
print((i));
i := i OVER 2
OD
Output:
+1024 +512 +256 +128 +64 +32 +16 +8 +4 +2 +1
[edit] AmigaE
PROC main()
DEF i = 1024
WHILE i > 0
WriteF('\d\n', i)
i := i / 2
ENDWHILE
ENDPROC
[edit] AppleScript
AppleScript does not natively support a standard out. Use the Script Editor's Event Log as the output.
set i to 1024
repeat while i > 0
log i
set i to i / 2
end repeat
[edit] AutoHotkey
i = 1024
While (i > 0)
{
output = %output%`n%i%
i := Floor(i / 2)
}
MsgBox % output
[edit] AWK
BEGIN {
v = 1024
while(v > 0) {
print v
v = int(v/2)
}
}
[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;
}
In for loop fashion:
int i;
for(i = 1024;i > 0; i/=2){
printf("%d\n", i);
}
[edit] C++
int i = 1024;
while(i > 0) {
std::cout << i << std::endl;
i /= 2;
}
Alternatively, it can be done with for:
for (int i = 1024; i>0; i /= 2)
std::cout << i << std::endl;
Indeed, in C++,
for (init; cond; update)
statement;
is equivalent to
{
init;
while (cond)
{
statement;
update;
}
}
[edit] C#
int i = 1024;
while(i > 0){
System.Console.WriteLine(i);
i /= 2;
}
[edit] Clojure
(while (> @i 0)
(println @i)
(dosync (ref-set i (quot @i 2))))</lisp>
=={{header|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>
With script:
<cfscript>
i = 1024;
while( i > 0 )
{
writeOutput( i + "< br/ >" );
}
</cfscript>
[edit] Common Lisp
(setq i 1024)
(loop while (> i 0) do
(print i)
(setq i (floor i 2)))
[edit] D
import std.stdio;
int i = 1024;
void main() {
while(i > 0) {
writefln("%s", i);
i >>= 1;
}
}
[edit] E
var i := 1024
while (i > 0) {
println(i)
i //= 2
}
[edit] Factor
1024 [ dup 0 > ] [ dup . 2 /i ] while drop
[edit] FALSE
1024[$0>][$."
"2/]#%
[edit] Forth
: halving ( n -- )
begin dup 0 >
while cr dup . 2/
repeat drop ;
1024 halving
[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 (when)
main = loop 1024
where loop n = when (n > 0)
(do print n
loop (n `div` 2))
You could try to write a "while" that operates on monads:
import Control.Monad (when)
whileM :: (Monad m) => m Bool -> m a -> m ()
whileM cond body = do c <- cond
when c (body >> whileM cond body)
You can use it like this
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))
[edit] Icon
procedure main()
local i
i := 1024
while write(0 < (i := i / 2))
end
[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).
monad define 1024
while. 0 < y do.
smoutput y
y =. <. -: y
end.
i.0 0
)
[edit] Java
int i = 1024;
while(i > 0){
System.out.println(i);
i >>= 1; //also acceptable: i /= 2;
}
With a for loop:
for(int i = 1024; i > 0;i /= 2 /*or i>>= 1*/){
System.out.println(i);
}
[edit] JavaScript
var n = 1024;
while (n>0) {
print(n);
n/=2;
}
[edit] Joy
DEFINE putln == put '\n putch.
1024 [0 >] [dup putln 2 /] while.
[edit] Lisaac
+ i : INTEGER;
i := 1024;
{ i > 0 }.while_do {
i.print;
'\n'.print;
i := i / 2;
};
[edit] Logo
make "n 1024
while [:n > 0] [print :n make "n :n / 2]
[edit] Lua
n = 1024
while n>0 do
print(n)
n = math.floor(n/2)
end
[edit] 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:
i = 1024;
While[i > 0,
Print[i];
i = Floor[i/2];
]
[edit] MATLAB
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.
i.html">i = 1024;
while (i.html">i > 0)
disp(i.html">i);
i.html">i = floor(i.html">i/2);
end
[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] Metafont
Metafont has no while loop, but it can be "simulated" easily.
a := 1024;
forever: exitif not (a > 0);
show a;
a := a div 2;
endfor
[edit] Modula-3
The usual module code and imports are omitted.
PROCEDURE DivBy2() =
VAR i: INTEGER := 1024;
BEGIN
WHILE i > 0 DO
IO.PutInt(i);
IO.Put("\n");
i := i DIV 2;
END;
END DivBy2;
[edit] MOO
i = 1024;
while (i > 0)
player:tell(i);
i /= 2;
endwhile
[edit] Nimrod
var n: int = 1024
while n > 0:
echo(n)
n = n div 2
[edit] Oberon-2
The usual module code and imports are ommited.
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] Octave
i = 1024;
while (i > 0)
disp(i)
i = floor(i/2);
endwhile
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.
[edit] Oz
Oz' for-loop can be used in a C-like manner:
for I in 1024; I>0; I div 2 do
{Show I}
end
Alternatively, we can use the while feature of the for-loop with a mutable variable:
declare
I = {NewCell 1024}
in
for while:@I > 0 do
{Show @I}
I := @I div 2
end
[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
my $n = 1024;
while ($n) {
print "$n\n";
$n = int $n / 2;
}
until (condition) is equivalent to while (not condition).
my $n = 1024;
until ($n <= 0) {
print "$n\n";
$n = int $n / 2;
}
[edit] Perl 6
Works with: Rakudo version #21 "Seattle"
my Int $n = 2 * 1024;
while $n = $n div 2 {
say $n;
}
until condition is equivalent to while not condition.
my Int $n = 2 * 1024;
until ($n = $n div 2) <= 0 {
say $n;
}
[edit] PHP
$i = 1024;
while ($i > 0) {
echo "$i\n";
$i >>= 1;
}
[edit] PicoLisp
(let N 1024
(while (gt0 N)
(println N)
(setq N (/ N 2)) ) )
[edit] Pike
int main(){
int i = 1024;
while(i > 0){
write(i + "\n");
i = i / 2;
}
}
[edit] PL/I
declare i fixed binary initial (1024);
do while (i>0);
put skip list (i);
i = i / 2;
end;
[edit] Pop11
lvars i = 1024;
while i > 0 do
printf(i, '%p\n');
i div 2 -> i;
endwhile;
[edit] PowerShell
$i = 1024
while ($i -gt 0) {
$i
$i /= 2
}
Since PowerShell automatically converts variables to other types to accommodate for operations the above loop does not stop at 1 like it would in other languages but loops for quite a while until the value is small enough to be considered 0. An explicit cast corrects this:
$i = 1024
while ($i -gt 0) {
$i
[int]$i /= 2
}
[edit] Prolog
while(0) :- !.
while(X) :- X>0,write(X), nl, X1 is X // 2, while(X1).
[edit] 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
[edit] Python
n = 1024
while n > 0:
print n
n //= 2
[edit] R
i <- 1024L
while(i > 0)
{
print(i)
i <- i %/% 2
}
[edit] 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
]
[edit] REXX
Using integer division % here:
i = 1024
do while i > 0
say i
i = i % 2
end
[edit] Ruby
i = 1024
while i > 0 do
puts i
i /= 2
end
The above can be written in one statement (using the return value of the Kernel#puts method: nil is false), but the readability suffers:
i = 1024
puts i or i /= 2 while i > 0
until condition is equivalent to while not condition.
i = 1024
until i <= 0 do
puts i
i /= 2
end
[edit] Scheme
(do ((n 1024 (quotient n 2)))
((<= n 0))
(display n)
(newline))
[edit] 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;
[edit] Slate
[| n | n: 1024.
[n isPositive] whileTrue:
[inform: number printString.
n: n // 2]] do
[edit] Smalltalk
number := 1024.
[ number > 0 ] whileTrue:
[ Transcript print: number; nl.
number := number // 2 ]
[edit] Standard ML
val n = ref 1024;
while !n > 0 do (
print (Int.toString (!n) ^ "\n");
n := !n div 2
)
But it is more common to write it in a tail-recursive functional style:
let
fun loop n =
if n > 0 then (
print (Int.toString n ^ "\n");
loop (n div 2)
) else ()
in
loop 1024
end
[edit] Suneido
i = 1024
while (i > 0)
{
Print(i)
i = (i / 2).Floor()
}
Output:
1024
512
256
128
64
32
16
8
4
2
1
[edit] Tcl
set i 1024
while {$i > 0} {
puts $i
set i [expr {$i / 2}]
}
[edit] TI-89 BASIC
Local i
1024 → i
While i > 0
Disp i
intDiv(i, 2) → i
EndWhile
[edit] UNIX Shell
Works with: Bourne Again SHell
x=1024
while [[ $x -gt 0 ]]; do
echo $x
x=$(( $x/2 ))
done
[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] 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.
#import nat
g = ~&h-> ^C/half@h ~&
#show+
main = %nP*=tx g <1024>
output:
1024 512 256 128 64 32 16 8 4 2 1
Explicit iteration has its uses but there are always alternatives. The same output is produced by the following main program using bit manipulation.
main = %nP*=tK33 1024
[edit] V
1024 [0 >] [
dup puts
2 / >int
] while
[edit] Vedit macro language
#1 = 1024
while (#1 > 0) {
Num_Type(#1)
#1 /= 2
}
or with for loop:
for (#1 = 1024; #1 > 0; #1 /= 2) {
Num_Type(#1)
}
[edit] Visual Basic .NET
Dim x = 1024
Do
Console.WriteLine(x)
x = x \ 2
Loop While x > 0
