Loops/While: Difference between revisions
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Underscore (talk | contribs) (Added Perl 6 and slightly edited Perl 5.) |
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=={{header|Perl}}== |
=={{header|Perl}}== |
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<lang perl>my $n = 1024; |
<lang perl>my $n = 1024; |
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while ($n |
while ($n) { |
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print "$n\n"; |
print "$n\n"; |
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$n |
$n = int $n / 2; |
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}</lang> |
}</lang> |
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<code>until (''condition'')</code> is equivalent to <code>while (not ''condition'')</code>. |
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<lang perl>my $n = 1024; |
<lang perl>my $n = 1024; |
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until ($n <= 0) { |
until ($n <= 0) { |
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print "$n\n"; |
print "$n\n"; |
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$n |
$n = int $n / 2; |
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}</lang> |
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=={{header|Perl 6}}== |
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{{works with|Rakudo|#21 "Seattle"}} |
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<lang perl6>my Int $n = 2 * 1024; |
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while $n = $n div 2 { |
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say $n; |
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} |
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</lang> |
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<code>until ''condition''</code> is equivalent to <code>while not ''condition''</code>. |
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<lang perl6>my Int $n = 2 * 1024; |
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until ($n = $n div 2) <= 0 { |
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say $n; |
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}</lang> |
}</lang> |
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Revision as of 17:09, 18 October 2009
You are encouraged to solve this task according to the task description, using any language you may know.
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.
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
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
AmigaE
<lang amigae>PROC main()
DEF i = 1024
WHILE i > 0
WriteF('\d\n', i)
i := i / 2
ENDWHILE
ENDPROC</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
<lang qbasic>i = 1024 while i > 0
print i i = i / 2
wend</lang>
Befunge
84*:*> :v
^/2.:_@
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 c>int i = 1024; while(i > 0){
System.Console.WriteLine(i); i /= 2;
}</lang>
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>
Common Lisp
<lang lisp>(setq i 1024) (loop while (> i 0) do
(print i) (setq i (floor i 2)))</lang>
D
<lang d>import std.stdio;
int i = 1024; void main() {
while(i > 0) {
writefln("%s", i);
i >>= 1;
}
}</lang>
E
<lang e>var i := 1024 while (i > 0) {
println(i) i //= 2
}</lang>
FALSE
1024[$0>][$." "2/]#%
Forth
<lang forth>
: halving ( n -- ) begin dup 0 > while cr dup . 2/ repeat drop ; 1024 halving
</lang>
Factor
1024 [ dup 0 > ] [ dup . 2 /i ] [ drop ] while
Fortran
<lang fortran>
INTEGER :: i = 1024 DO WHILE (i > 0) WRITE(*,*) i i = i / 2 END DO
</lang>
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
<lang icon>
procedure main() local i i := 1024 while write(0 < (i := i / 2)) end
</lang>
J
J is array-oriented, so there is very little need for loops. For example, one could satisfy this task this way:
<lang j>
,. <.@-:^:*^:a: 1024
</lang>
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>
3 : 0 ] 1024
while. 0 < y do.
y 1!:2 ] 2
y =. <. -: y
end.
i. 0 0
)
</lang>
Though it's rare to see J code like this.
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 [0 >] [dup putln 2 /] while. </lang>
Lisaac
<lang Lisaac> + i : INTEGER; i := 1024; { i > 0 }.while_do {
i.print; '\n'.print; i := i / 2;
}; </lang>
Logo
make "n 1024 while [:n > 0] [print :n make "n :n / 2]
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>
MAXScript
a = 1024
while a > 0 do
(
print a
a /= 2
)
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
Metafont
Metafont has no a 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>
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>
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>
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.
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
<lang perl6>my Int $n = 2 * 1024; while $n = $n div 2 {
say $n;
} </lang>
until condition is equivalent to while not condition.
<lang perl6>my Int $n = 2 * 1024; until ($n = $n div 2) <= 0 {
say $n;
}</lang>
PHP
<lang php>$i = 1024; while ($i > 0) {
echo "$i\n"; $i >>= 1;
}</lang>
Pop11
lvars i = 1024;
while i > 0 do
printf(i, '%p\n');
i div 2 -> i;
endwhile;
PowerShell
<lang powershell>$i = 1024 while ($i -gt 0) {
$i $i /= 2
}</lang> Since PowerShell automatically converts variables to other types to accommodate for operations the above loop does not stop at 1 like it would in other languages but loops for quite a while until the value is small enough to be considered 0. An explicit cast corrects this: <lang powershell>$i = 1024 while ($i -gt 0) {
$i [int]$i /= 2
}</lang>
Prolog
<lang prolog>while(0) :- !. while(X) :- write(X), nl, X1 is X // 2, while(X1).</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>
Ruby
<lang ruby>i = 1024 while i > 0 do
puts i i /= 2
end</lang> Ruby also has a "while" statement modifier: <lang ruby>i = 1024 begin puts i; i /= 2; end while i > 0</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>
Scheme
<lang scheme> (do ((n 1024 (quotient n 2)))
((<= n 0)) (display n) (newline))</lang>
Slate
<lang slate> [| n | n: 1024.
[n isPositive] whileTrue:
[inform: number printString.
n: n // 2]] do
</lang>
Smalltalk
<lang smalltalk>number := 1024. [ number > 0 ] whileTrue:
[ 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>
Tcl
<lang tcl>set i 1024 while {$i > 0} {
puts $i
set i [expr {$i / 2}]
}</lang>
TI-89 BASIC
Local i 1024 → i While i > 0 Disp i intDiv(i, 2) → i EndWhile
UNIX Shell
<lang bash>x=1024 while $x -gt 0 ; do
echo $x x=$(( $x/2 ))
done</lang>
UnixPipes
<lang sh> (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:
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. <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>
- Programming Tasks
- Iteration
- ActionScript
- Ada
- ALGOL 68
- AmigaE
- AutoHotkey
- AWK
- BASIC
- Befunge
- C
- C++
- C sharp
- ColdFusion
- Common Lisp
- D
- E
- FALSE
- Forth
- Factor
- Fortran
- Haskell
- Icon
- J
- Java
- JavaScript
- Joy
- Lisaac
- Logo
- Mathematica
- MAXScript
- Make
- Metafont
- Modula-3
- MOO
- Oberon-2
- OCaml
- Octave
- Pascal
- Perl
- Perl 6
- PHP
- Pop11
- PowerShell
- Prolog
- Python
- R
- Ruby
- Scheme
- Slate
- Smalltalk
- Standard ML
- Tcl
- TI-89 BASIC
- UNIX Shell
- UnixPipes
- Ursala
- V
- Vedit macro language
- Visual Basic .NET