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.

ActionScript

<lang actionscript>var val:int = 0; do {

   trace(++val);

} while (val % 6);</lang>

Ada

<lang ada>loop

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

end loop;</lang> Here is an alternative version: <lang ada>for Value in 0..Integer'Last loop

  Put (Value);
  exit when Value mod 6 = 0;

end loop;</lang>

ALGOL 68

<lang algol68>FOR value WHILE

 print(value);

1. WHILE # value MOD 6 /= 0 DO

 SKIP

OD</lang>

AmigaE

<lang amigae>PROC main()

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

ENDPROC</lang>

AutoHotkey

<lang AutoHotkey>While mod(A_Index, 6) ;comment:everything but 0 is considered true

 output = %output%`n%A_Index%

MsgBox % output</lang>

AWK

<lang awk>BEGIN {

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

}</lang>

BASIC

Works with: QuickBasic version 4.5

<lang qbasic>a = 0 do

 a = a + 1
 print a

loop while a mod 6 <> 0</lang>

Befunge

<lang befunge>0>1+:.v

|%6: <
@</lang>

C

<lang c>int val = 0; do{

  val++;
  printf("%d\n",val);

}while(val % 6 != 0);</lang>

C++

<lang cpp>int val = 0; do{

  val++;
  cout << val << endl;

}while(val % 6 != 0);</lang>

C#

<lang csharp>int a = 0;

do {

   Console.WriteLine(a);
   a += 1;

} while (a % 6 != 0);</lang>

ColdFusion

<lang cfm><cfscript>

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

</cfscript></lang>

Common Lisp

<lang lisp>(setq val 0) (loop do

 (incf val)
 (print val)
while (/= 0 (mod val 6)))</lang>

D

<lang d>int val = 0; do{

 val++;
 writefln(val);

}while(val % 6 != 0);</lang>

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. <lang e>var x := 0 __loop(fn {

   x += 1
   println(x)
   x % 6 != 0   # this is the return value of the function

})</lang>

Factor

<lang factor>0 [ dup 6 mod 0 = not ] [ [ . ] [ 1 + ] bi ] do while drop</lang>

Forth

<lang forth>: do-until

 0
 begin 1+
       dup .
       dup 6 mod 0=
 until
 drop ;</lang>

Fortran

Works with: Fortran version 90 and later

<lang fortran>INTEGER :: i = 0 DO

 i = i + 1
 WRITE(*, *) i
 IF (MOD(i, 6) == 0) EXIT

END DO</lang>

Haskell

<lang haskell>import Data.List import Control.Monad import Control.Arrow

doWhile p f n = (n:) $ takeWhile p $ unfoldr (Just.(id &&& f)) $ succ n</lang> Example executed in GHCi: <lang haskell>*Main> mapM_ print $ doWhile ((/=0).(`mod`6)) succ 0 0 1 2 3 4 5</lang>

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). <lang j>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
  )</lang>

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

Java

<lang java>int val = 0; do{

  val++;
  System.out.println(val);

}while(val % 6 != 0);</lang>

JavaScript

<lang javascript>var val = 0; do {

 print(++val);

} while (val % 6);</lang>

Lua

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

<lang lua> i=0 repeat

 i=i+1
 print(i)

until i%6 == 0 </lang>

Lisaac

<lang Lisaac>+ val : INTEGER; {

 val := val + 1;
 val.print;
 '\n'.print;
 val % 6 != 0

}.while_do { };</lang>

Logo

<lang 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</lang>

Mathematica

<lang Mathematica>value = 5; NestWhile[

 # + 1 &
 ,
 value
 , (Print[#]; Mod[#, 6] != 0) &
 ];</lang>

gives back: <lang Mathematica>5 6</lang> If the starting value is 6, only 6 is returned.

MAXScript

<lang maxscript>a = 0 do (

   print a
   a += 1

) while mod a 6 != 0</lang>

Metafont

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

<lang metafont>a := 0; forever: show a; a := a + 1; exitif a mod 6 = 0; endfor end</lang>

OCaml

OCaml doesn't have a do-while loop, so we can just make a local loop: <lang ocaml>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</lang>

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

<lang ocaml>let do_while f p =

 let rec loop() =
   f();
   if p() then loop()
 in
 loop()

(** val do_while : (unit -> 'a) -> (unit -> bool) -> unit *)</lang>

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

        (fun () -> !v mod 6 <> 0)</lang>

The example above is the an imperative form, below is its functional counterpart: <lang ocaml>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</lang>

Or in a very poor OCaml style, we can use an exception to exit a while loop: <lang ocaml>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 -> ()</lang>

Octave

The do-while can be changed into a do-until, just negating the condition of the while. <lang octave>val = 0; do

 val++;
 disp(val)

until( mod(val, 6) == 0 )</lang>

Oz

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

 I = {NewCell 0}

in

 for until:@I mod 6 == 0 do
    I := @I + 1
    {Show @I}
 end</lang>

Pascal

<lang pascal>program countto6(output);

var

 i: integer;

begin

 i := 0;
 repeat
   i := i + 1;
   writeln(i)
 until i mod 6 = 0

end.</lang>

Perl

<lang perl>my $val = 0; do {

  $val++;
  print "$val\n";

} while ($val % 6);</lang> do ... until (condition) is equivalent to do ... while (not condition). <lang perl>my $val = 0; do {

  $val++;
  print "$val\n";

} until ($val % 6 == 0);</lang>

Perl 6

Works with: Rakudo version #21 "Seattle"

<lang perl6>my $val = 0; repeat {

   say ++$val;

} while $val % 6;</lang>

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

<lang perl6>my $val = 0; repeat {

   say ++$val;

} until $val % 6 == 0;</lang>

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

<lang perl6>my $val = 0; repeat while $val % 6 {

   say ++$val;

}</lang>

PHP

<lang php>$val = 0; do {

  $val++;
  print "$val\n";

} while ($val % 6 != 0);</lang>

Pike

<lang pike>int main(){

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

}</lang>

Pop11

<lang pop11>lvars val = 0; while true do

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

endwhile;</lang>

PowerShell

<lang powershell>$n = 0 do {

   $n++
   $n

} while ($n % 6 -ne 0)</lang>

Python

Python doesn't have a do-while loop. <lang python>val = 0 while True:

  val +=1
  print val
  if val % 6 == 0: break</lang>

or repeat the body of the loop before a standard while. <lang python>val = 1 print val while val % 6 != 0:

  val += 1
  print val</lang>

R

<lang R>i <- 0 repeat {

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

}</lang>

REBOL

<lang 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 ]</lang>

Output:

1
2
3
4
5
6

REXX

In the do until construct, the expression is evaluated at the end, even though it is written at the beginning. <lang rexx>v = 0 do until v//6 = 0

 v = v + 1
 say v

end</lang>

Ruby

<lang ruby>val = 0 begin

  val += 1
  puts val

end while val % 6 != 0</lang>

begin ... end until condition is equivalent to begin ... end while not condition. <lang ruby>val = 0 begin

  val += 1
  puts val

end until val % 6 == 0</lang>

Slate

<lang slate>[| val |

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

] do.</lang>

Smalltalk

To simulate the do-while construct, we can use the whileTrue: method of a block with a void while block. <lang smalltalk>|val| val := 0. [

 val := val + 1.
 val displayNl.
 (val rem: 6) ~= 0

] whileTrue: [ ]</lang>

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 <lang tcl>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}</lang>

The control package of

Library: tcllib

has this:

<lang tcl>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}</lang>

Mind you, it is also normal to write this task using a normal while as: <lang tcl>set i 0 while true {

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

}</lang>

Vedit macro language

<lang vedit>#1 = 0 do {

   #1++
   Num_Type(#1)

} while (#1 % 6 != 0);</lang>

Visual Basic .NET

<lang vbnet>Dim i = 0 Do

   i += 1
   Console.WriteLine(i)

Loop Until i Mod 6 = 0</lang>