Loops/Do-while

From Rosetta Code

Start with a value at 0. Loop while value mod 6 is not equal to 0. Each time through the loop, add 1 to the value then print it. The loop must execute at least once.

[edit] ActionScript

var val:int = 0;
do 
{
    trace(++val);
} while (val % 6);

[edit] Ada

loop
   Value := Value + 1;
   Put (Value);
   exit when Value mod 6 = 0;
end loop;

Here is an alternative version:

for Value in 0..Integer'Last loop
   Put (Value);
   exit when Value mod 6 = 0;
end loop;

[edit] ALGOL 68

FOR value WHILE
  print(value);
# WHILE # value MOD 6 /= 0 DO 
  SKIP
OD

[edit] AmigaE

PROC main()
  DEF i = 0
  REPEAT
    i := i + 1
    WriteF('\d\n', i)
  UNTIL Mod(i, 6) = 0
ENDPROC

[edit] AutoHotkey

While mod(A_Index, 6) ;comment:everything but 0 is considered true
  output = %output%`n%A_Index%
MsgBox % output

[edit] AWK

BEGIN {
  val = 0
  do {
    val++
    print val
  } while( val % 6 != 0)
}

[edit] BASIC

Works with: QuickBasic version 4.5

a = 0
DO
  a = a + 1
  PRINT a
LOOP WHILE a MOD 6 <> 0

[edit] Befunge

0>1+:.v
 |%6: <
 @

[edit] C

int val = 0;
do{
   val++;
   printf("%d\n",val);
}while(val % 6 != 0);

[edit] C++

int val = 0;
do{
   val++;
   cout << val << endl;
}while(val % 6 != 0);

[edit] C#

int a = 0;
 
do
{
    Console.WriteLine(a);
    a += 1;
} while (a % 6 != 0);

[edit] ColdFusion

<cfscript>
  value = 0;
  do
  {
    value += 1;
    writeOutput( value );
  } while( value % 6 != 0 );			
</cfscript>

[edit] Common Lisp

(setq val 0)
(loop do
  (incf val)
  (print val)
 while (/= 0 (mod val 6)))

[edit] D

int val = 0;
do{
  val++;
  writefln(val);
}while(val % 6 != 0);

E does not have an official do-while construct, but the primitive which loops are built out of (which calls a function which returns a boolean indicating whether it should be called again) can be used to construct a do-while.

var x := 0
__loop(fn {
    x += 1
    println(x)
    x % 6 != 0   # this is the return value of the function
})

[edit] Factor

0 [ dup 6 mod 0 = not ] [ [ . ] [ 1 + ] bi ] do while drop

[edit] Forth

: do-until
  0
  begin 1+
        dup .
        dup 6 mod 0=
  until
  drop ;

[edit] Fortran

Works with: Fortran version 90 and later

INTEGER :: i = 0
DO 
  i = i + 1
  WRITE(*, *) i
  IF (MOD(i, 6) == 0) EXIT
END DO

[edit] Haskell

import Data.List
import Control.Monad
import Control.Arrow
 
doWhile p f n = (n:) $ takeWhile p $ unfoldr (Just.(id &&& f)) $ succ n

Example executed in GHCi:

*Main> mapM_ print $ doWhile ((/=0).(`mod`6)) succ 0
0
1
2
3
4
5

[edit] J

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

  ,. ([^:(0=6|])>:)^:a: 0

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 ] 0
 
         NB.  The 'st' in 'whilst' stands for 'skip test'
 
         whilst. 0 ~: 6 | y do.  
             y 1!:2 ]2 
             y =. y+1
         end.
 
        i.0 0
   )

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

[edit] Java

int val = 0;
do{
   val++;
   System.out.println(val);
}while(val % 6 != 0);

[edit] JavaScript

var val = 0;
do {
  print(++val);
} while (val % 6);

[edit] Lua

Lua doesn't have a do .. while construct.

 
i=0
repeat
  i=i+1
  print(i)
until i%6 == 0

[edit] Lisaac

+ val : INTEGER;
{
  val := val + 1;
  val.print;
  '\n'.print;
  val % 6 != 0
}.while_do { };

[edit] Logo

make "val 0
do.while [make "val :val + 1  print :val] [notequal? 0 modulo :val 6]
do.until [make "val :val + 1  print :val] [equal? 0 modulo :val 6]
 
to my.loop :n
  make "n :n + 1
  print :n
  if notequal? 0 modulo :n 6 [my.loop :n]
end
my.loop 0

[edit] Mathematica

value = 5;
NestWhile[
  # + 1 &
  ,
  value
  , (Print[#]; Mod[#, 6] != 0) &
  ];

gives back:

5
6

If the starting value is 6, only 6 is returned.

[edit] MAXScript

a = 0
do
(
    print a
    a += 1
)
while mod a 6 != 0

[edit] Metafont

Metafont has no a do-while construct; the same thing can be done using a forever loop and exitif.

a := 0;
forever: show a; a := a + 1; exitif a mod 6 = 0; endfor
end

[edit] OCaml

OCaml doesn't have a do-while loop, so we can just make a local loop:

let rec loop i =
  let i = succ i in
  Printf.printf "%d\n" i;
  if i mod 6 <> 0 then
    loop i
  in
  loop 0

or implementing a generic do-while iterator with higher order function:

let do_while f p =
  let rec loop() =
    f();
    if p() then loop()
  in
  loop()
(** val do_while : (unit -> 'a) -> (unit -> bool) -> unit *)

let v = ref 0 in
do_while (fun () -> incr v; Printf.printf "%d\n" !v)
         (fun () -> !v mod 6 <> 0)

The example above is the an imperative form, below is its functional counterpart:

let do_while f p ~init =
  let rec loop v =
    let v = f v in
    if p v then loop v
  in
  loop init
 
do_while (fun v ->
            let v = succ v in
            Printf.printf "%d\n" v;
            (v))
         (fun v -> v mod 6 <> 0)
         ~init:0

Or in a very poor OCaml style, we can use an exception to exit a while loop:

let v = ref 0
exception Exit_loop
try while true do
  incr v;
  Printf.printf "%d\n" !v;
  if not(!v mod 6 <> 0) then
    raise Exit_loop;
done
with Exit_loop -> ()

[edit] Octave

The do-while can be changed into a do-until, just negating the condition of the while.

val = 0;
do
  val++;
  disp(val)
until( mod(val, 6) == 0 )

[edit] Oz

Normal Oz variables are single-assignment only. So we use a "cell", which is a one-element mutable container.

declare
  I = {NewCell 0}
in
  for until:@I mod 6 == 0 do
     I := @I + 1
     {Show @I}
  end

[edit] Pascal

program countto6(output);
 
var
  i: integer;
 
begin
  i := 0;
  repeat
    i := i + 1;
    writeln(i)
  until i mod 6 = 0
end.

[edit] Perl

my $val = 0;
do {
   $val++;
   print "$val\n";
} while ($val % 6);

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

my $val = 0;
do {
   $val++;
   print "$val\n";
} until ($val % 6 == 0);

[edit] Perl 6

Works with: Rakudo version #21 "Seattle"

my $val = 0;
repeat {
    say ++$val;
} while $val % 6;

repeat ... until condition is equivalent to do ... while not condition.

my $val = 0;
repeat {
    say ++$val;
} until $val % 6 == 0;

You can also put the condition before the block, without changing the order of evaluation.

my $val = 0;
repeat while $val % 6 {
    say ++$val;
}

[edit] PHP

$val = 0;
do {
   $val++;
   print "$val\n";
} while ($val % 6 != 0);

[edit] PicoLisp

Literally:

(let Val 0
   (loop
      (println (inc 'Val))
      (T (=0 (% Val 6))) ) )

Shorter:

(let Val 0
   (until (=0 (% (println (inc 'Val)) 6))) )

or:

(for (Val 0  (n0 (% (println (inc 'Val)) 6))))

[edit] Pike

int main(){
   int value = 0;
   do {
      value++;
      write(value + "\n");
   } while (value % 6);
}

[edit] PL/I

 
value = 0;
do value = 0, value+1 while (mod(value,6) ^= 0);
   put list (value);
end;

[edit] Pop11

lvars val = 0;
while true do
   val + 1 -> val;
   printf(val, '%p\n');
   quitif(val rem 6 = 0);
endwhile;

[edit] PowerShell

$n = 0
do {
    $n++
    $n
} while ($n % 6 -ne 0)

[edit] PureBasic

Works with: PureBasic version 4.41

x=0
Repeat
  x+1
  Debug x
Until x%6=0

[edit] Python

Python doesn't have a do-while loop.

val = 0
while True:
   val +=1
   print val
   if val % 6 == 0: break

or repeat the body of the loop before a standard while.

val = 1
print val
while val % 6 != 0:
   val += 1
   print val

[edit] R

i <- 0
repeat
{
   i <- i + 1
   print(i)
   if(i %% 6 == 0) break
}

[edit] REBOL

rebol [
	Title: "Loop/While"
	Author: oofoe
	Date: 2009-12-19
	URL: http://rosettacode.org/wiki/Loop/Do_While
]
 
; REBOL doesn't have a specific 'do/while' construct, but 'until' can
; be used to provide the same effect.
 
value: 0
until [
	value: value + 1
	print value
 
	0 = mod value 6
]

Output:

[edit] REXX

In the do until construct, the expression is evaluated at the end, even though it is written at the beginning.

v = 0
do until v//6 = 0
  v = v + 1
  say v
end

[edit] Ruby

val = 0
begin
   val += 1
   puts val
end while val % 6 != 0

begin ... end until condition is equivalent to begin ... end while not condition.

val = 0
begin
   val += 1
   puts val
end until val % 6 == 0

[edit] Scheme

(let loop ((i 1))
  (display i)
  (if (positive? (modulo i 6))
      (loop (+ i 1))))

[edit] Seed7

$ include "seed7_05.s7i";
 
const proc: main is func
  local
    var integer: number is 0;
  begin
    repeat
      incr(number);
      writeln(number)
    until number rem 6 = 0
  end func;

[edit] Slate

[| val |
  val: 0.
  [val: val + 1.
   print: val.
   val \\ 6 ~= 0] whileTrue
] do.

[edit] Smalltalk

To simulate the do-while construct, we can use the whileTrue: method of a block with a void while block.

|val|
val := 0.
[ 
  val := val + 1.
  val displayNl.
  (val rem: 6) ~= 0
] whileTrue: [ ]

[edit] Suneido

val = 0
do
    {
    Print(++val)
    } while (val % 6 isnt 0)