Loops/Do-while

Loops/Do-while
You are encouraged to solve this task according to the task description, using any language you may know.

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.

6502 Assembly

Code is called as a subroutine (i.e. JSR DoWhileSub). Specific OS/hardware routines for printing are left unimplemented.

DoWhileSub:	PHA
		TYA
		PHA			;push accumulator and Y register onto stack
 
		LDY #0
DoWhileLoop:	INY
		JSR DisplayValue	;routine not implemented
		TYA
		SEC
Modulus:	SBC #6
		BCS Modulus
		ADC #6
		BNE DoWhileLoop
 
		PLA
		TAY
		PLA			;restore Y register and accumulator from stack
		RTS			;return from subroutine

ActionScript

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

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;

Aime

integer a;
 
a = 0;
do {
   a += 1;
   o_integer(a);
   o_byte('\n');
} while (a % 6 != 0);

ALGOL 68

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

AmigaE

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

AutoHotkey

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

AWK

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

BASIC

Works with: QuickBasic version 4.5

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

BBC BASIC

a = 0
REPEAT
  a = a + 1
  PRINT a
UNTIL a MOD 6 = 0

bc

i = 0
for (;;) {
	++i	/* increments then prints i */
	if (i % 6 == 0) break
}
quit

Befunge

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

C

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

C++

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

C#

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

CoffeeScript

CoffeeScript doesn't have do {} while () loop, but it can be emulated using loop statement and break unless statement.

val = 0
loop
  console.log ++val
  break unless val % 6

ColdFusion

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

Common Lisp

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

loop can set up temporary values, and incf returns a value, so it's also possible to do

(loop with val = 0
      do (print (incf val))
      until (= 0 (mod val 6)))

Clojure

(loop [i 0]
  (let [i* (inc i)]
    (println i*)
    (when-not (zero? (mod i* 6))
      (recur i*))))

D

import std.stdio;
 
void main() {
    int val;
    do {
        val++;
        write(val, " ");
    } while (val % 6 != 0);
}

Output:

1 2 3 4 5 6 

dc

Translation of: bc

0 si		[i = 0]sz
[2Q]sA		[A = code to break loop]sz
[
 li 1 + p	[print it = i + 1]sz
 d si		[i = it, leave it on stack]sz
 6 % 0 =A	[call A if 0 == it % 6]sz
 0 0 =B		[continue loop]sz
]sB 0 0 =B

Delphi

program Loop;
 
{$APPTYPE CONSOLE}
 
var
  I: Integer;
 
begin
  I:= 0;
  repeat
    Inc(I);
    Write(I:2);
  until I mod 6 = 0;
  Writeln;
  Readln;
end.

DWScript

 
var i := 0;
 
repeat
   Inc(i);
   PrintLn(i);
until i mod 6 = 0;
 

E

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
})

Ela

open console
 
loop n | n % 6 == 0 = out ()
       | else = out `seq` loop (n+1)
        where out = & writen n

This implementation uses a thunk to represent a console output. Output is not done in the initialization of 'out' variable, it is done when 'out' calculation is forced by a 'seq' operator (sequencing operator).

Erlang

 
do() ->
	io:format("0~n"),
	do(1).
 
do(N) when N rem 6 =:= 0 ->
	io:format("~w~n", [N]);
do(N) ->
	io:format("~w~n", [N]),
	do(N+1).
 

Factor

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

Fantom

There is no do-while statement in Fantom, so instead use an infinite while loop with a break statement:

 
class Main
{
  public static Void main ()
  {
    i := 0
    while (true)
    {
      i += 1
      echo (i)
      if (i % 6 == 0) break // end loop on condition
    }
  }
}
 

Forth

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

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

Works with: Fortran version 77 and later

      PROGRAM DOWHILE
C Initialize modulus and value.
        INTEGER MODLUS, IVALUE
        PARAMETER (MODLUS = 6)
        IVALUE = 0
 
C FORTRAN 77 has no do-while structure -- not semantically. It is not
C difficult to simulate it using GOTO, however:
   10   CONTINUE
          IVALUE = IVALUE + 1
          WRITE (*,*) IVALUE
        IF (.NOT. (MOD(IVALUE, MODLUS) .EQ. 0)) GOTO 10
 
        STOP
      END

Go

No do-while in Go.

package main
 
import "fmt"
 
func main() {
    for value := 0;; {
        value++
        fmt.Println(value)
        if value % 6 == 0 {
            break
        }
    }
}

Output:

1
2
3
4
5
6

GML

i = 0
do
    {
    i += 1
    show_message(string(i))
    }
until (i mod 6 = 0)

Groovy

Groovy does not have a bottom-checking loop construct! So use an "infinite" while loop with a conditional break as the last statement

def i = 0
while (true) {
    i++
    println i
    if ( i % 6 == 0) break
}

Output:

1
2
3
4
5
6

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

Icon and Unicon

Icon and Unicon do not have a do-while looping control with end of loop checking. There are four looping controls 'every', 'repeat', 'until', and 'while' (see Introduction to Icon and Unicon/Looping Controls for more information.)

procedure main()
 
i := 0
repeat {
   write(i +:= 1)
   if i % 6 = 0 then break
   }
end

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.

Java

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

JavaScript

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

LabVIEW

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.

Liberty BASIC

 
a = 0
do
  a =a +1
  print a
loop until ( a mod 6) = 0
 

Lisaac

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

Lua

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

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

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

Maple

val := 0:
do
        val := 1 + val;
        print( val );
        if irem( val, 6 ) = 0 then
                break
        end if;
end do:

Mathematica

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

gives back:

5
6

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

MATLAB / Octave

   a=0; 
   while (1) 
      a = a+1; 
      disp(a);
   if (~mod(a,6)) break; end; 	
   end; 

Maxima

block([n: 0], do (ldisp(n: n + 1), if mod(n, 6) = 0 then return('done)))$

MAXScript

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

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

МК-61/52

0	П4	КИП4	ИП4	6	/	{x}	x=0	02	С/П

Modula-2

MODULE DoWhile;
  IMPORT InOut;
 
  VAR
    i: INTEGER;
 
BEGIN
  i := 0
  REPEAT
    InOut.WriteInt(i, 1);
    InOut.WriteLn;
    INC(i)
  UNTIL i MOD 6 = 0;
END DoWhile.

Modula-3

This is very similar to the Modula-2 code above.

REPEAT
  i := i + 1;
  IO.Put(Fmt.Int(i));
UNTIL i MOD 6 = 0;

Nemerle

mutable x = 0;
do
{
    x++;
    WriteLine($"$x");
} while (x % 6 != 0)

NetRexx

In NetRexx the do–while construct is implemented via the until expru conditional clause of the loop instruction. The expression expru in the until expru clause is evaluated at the end of the loop, guaranteeing that the loop will be executed at least once.

/* NetRexx */
options replace format comments java crossref savelog symbols nobinary
 
  say
  say 'Loops/Do-while'
 
  i_ = 0
  loop until i_ // 6 = 0
    i_ = i_ + 1
    say i_
    end
 

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 -> ()

Objeck

 
i := 0;
do {
   i += 1;
   i->PrintLine();
} 
while (i % 6 <> 0);
 

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 )

Openedge/Progress

DEFINE VARIABLE ii AS INTEGER.
 
DO WHILE ii MODULO 6 <> 0 OR ii = 0:
   ii = ii + 1.
   MESSAGE ii VIEW-AS ALERT-BOX.
END.

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

PARI/GP

The generic Pari loops (while, until) test at the beginning, so just use an infinite loop with a break.

x = 0;
while(1,
  print(x++);
 if(val % 6 == 0, break)
)

Pascal

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

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);

Perl 6

Works with: Rakudo Star version 2010.08

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;

(Here we've used %%, the "divisible-by" operator.)

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

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

PHP

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

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))))

Pike

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

PL/I

 
dcl value fixed bin (31) init (0);     
do forever;                            
  value = value + 1;                   
 
  if mod(value, 6) = 0 then            
    leave;                             
 
  put list (value);                    
end;                                   
 

or shorter:

 
 dcl value fixed bin(31) init(0);
 do Until(value=6);
   value+=1;
   put Skip list(value);
 end;

Output:

             1
             2
             3
             4
             5
             6     

Pop11

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

PowerShell

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

Prolog

 
% initial condition
do(0):- write(0),nl,do(1).
 
% control condition
do(V):- 0 is mod(V,6), !, fail.
 
% loop
do(V) :-
    write(V),nl,
    Y is V + 1,
    do(Y).
 
wloop :-
   do(0).
 
 

PureBasic

Works with: PureBasic version 4.41

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

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

R

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

Racket

Idiomatic Racket code is functional:

 
#lang racket
(let loop ([n 0])
  (let ([n (add1 n)])
    (displayln n)
    (unless (zero? (modulo n 6)) (loop n))))
 

But an imperative version is easy to do too:

 
#lang racket
(define n 0)
(let loop ()
  (set! n (add1 n))
  (displayln n)
  (unless (zero? (modulo n 6)) (loop)))
 

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:

1
2
3
4
5
6

REXX

In the DO UNTIL construct, the expression is evaluated at the end of the DO loop,
even though it is written at the beginning.
This insures that the DO UNTIL loop will execute at least once (as coded below).

In contrast, a DO WHILE construct, the expression would be evaluated at the beginning of the DO loop, and
may cause the DO WHILE loop to not execute at all.
This necessitates the use of DO UNTIL instead of DO WHILE.

version 1

/*REXX program to demonstrate a  DO  UNTIL  construction.               */
 
v=0
          do  until  v//6 == 0
          v=v+1
          say v
          end
                                       /*stick a fork in it, we're done.*/

output

1
2
3
4
5
6

version 2

/*REXX program to demonstrate a  DO  UNTIL  construction.               */
 
          do v=1  until  v//6==0
          say v
          end
                                       /*stick a fork in it, we're done.*/

output is the same as the 1^st version.

Ruby

The while statement modifier normally checks the condition before entering the loop. But if the while statement modifier is on a begin ... end statement, then it loops at least once. Same with the until statement modifier.

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

During November 2005, Yukihiro Matsumoto, the creator of Ruby, regretted this loop feature and suggested using Kernel#loop.

break unless	break if
val = 0 loop do val += 1 puts val break unless val %6 != 0 end	val = 0 loop do val += 1 puts val break if val %6 == 0 end

All four of these examples print the numbers 1, 2, 3, 4, 5, 6.

Salmon

variable x := 0;
do
  {
    ++x;
    x!
  }
while (x % 6 != 0);

SAS

/* using DO UNTIL so that the loop executes at least once */
data _null_;
n=0;
do until(mod(n,6)=0);
  n=n+1;
  put n;
end;
run;

Sather

Translation of: C

class MAIN is
  main is
    val ::= 0;
    loop
      val := val + 1;
      #OUT + val + "\n";
      while!(val % 6 /= 0)
    end;
  end;
end;

Scala

var x=0
do {
  println(x)
  x+=1
} while(x%6!=0)

Scheme

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

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;

Slate

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

Smalltalk

Works with: Smalltalk/X

Works with: VisualWorks Smalltalk

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

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

Works with: GNU 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: [ ]

Suneido

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

Output:

1
2
3
4
5
6

Tcl

Tcl does not have a built-in do...while construct. This example demonstrates the ease of creating new looping contructs in plain Tcl. do procedure taken from Tcler's wiki

proc do {body keyword expression} {
    if {$keyword eq "while"} {
       set expression "!($expression)"
    } elseif {$keyword ne "until"} {
       return -code error "unknown keyword \"$keyword\": must be until or while"
    }
    set condition [list expr $expression]
    while 1 {
       uplevel 1 $body
       if {[uplevel 1 $condition]} {
          break
       }
    }
    return
}
 
set i 0
do {puts [incr i]} while {$i % 6 != 0}

Library: Tcllib (Package: control)

package require control
set i 0; control::do {puts [incr i]} while {$i % 6 != 0}
set i 0; control::do {puts [incr i]} until {$i % 6 == 0}

Mind you, it is also normal to write this task using a normal while as:

set i 0
while true {
    puts [incr i]
    if {$i % 6 == 0} break
}

TUSCRIPT

 
$$ MODE TUSCRIPT
var=0
LOOP
var=var+1, rest=var%6
PRINT var
IF (rest==0) EXIT
ENDLOOP
 

Output:

1
2
3
4
5
6

UNIX Shell

Works with: bash

Works with: pdksh

Works with: zsh

val=0
while true; do
  echo $((++val))
  [ $((val%6)) -eq 0 ] && break
done

Works with: Bourne Shell

val=0
while true; do
  val=`expr $val + 1`
  echo $val
  expr $val % 6 = 0 >/dev/null && break
done

Vedit macro language

#1 = 0
do {
    #1++
    Num_Type(#1)
} while (#1 % 6 != 0);

Visual Basic .NET

Dim i = 0
Do
    i += 1
    Console.WriteLine(i)
Loop Until i Mod 6 = 0

XPL0

code CrLf=9, IntOut=11;
int V;
[V:= 0;
repeat  V:= V+1;
        IntOut(0, V);  CrLf(0);
until   rem(V/6) = 0;
]

Yorick

val = 0;
do {
    val++;
    write, val;
} while(val % 6 != 0);