Loops/Infinite

From Rosetta Code
Task
Loops/Infinite
You are encouraged to solve this task according to the task description, using any language you may know.
Specifically print out "SPAM" followed by a newline in an infinite loop.

4DOS Batch

<lang 4dos>@echo off do forever

 echo SPAM

enddo</lang>

6502 Assembly

Specific OS/hardware routines for printing are left unimplemented. <lang 6502asm>InfiniteLoop LDX #0 PrintLoop: LDA MSG,x JSR PrintAccumulator ;routine not implemented INX CPX #5 BNE PrintLoop JMP InfiniteLoop

MSG .byte "SPAM", $0A</lang>

ActionScript

<lang actionscript>while (true) {

   trace("SPAM");

}</lang>

Ada

<lang ada>loop

  Put_Line("SPAM");

end loop;</lang>

ALGOL 68

<lang algol68>DO

 printf($"SPAM"l$)

OD</lang> Or the classic "dynamic halt": <lang algol68>loop x:

  printf($"SPAM"l$);

loop x</lang>

AmigaE

<lang amigae>PROC main()

 LOOP
   WriteF('SPAM')
 ENDLOOP

ENDPROC</lang>

AutoHotkey

<lang autohotkey>Loop

 MsgBox SPAM `n</lang>

AWK

<lang awk>BEGIN {

 while(1) {
   print "SPAM"
 }

}</lang>

Bash

<lang bash>while true; do echo "SPAM"; done</lang> <lang bash>until false; do echo "SPAM"; done</lang> <lang bash>for ((;;)); do echo "SPAM"; done</lang>

BASIC

Works with: QuickBasic version 4.5

Old-fashioned syntax: <lang qbasic>while 1

 print "SPAM"

wend</lang>

Standard BASIC: <lang qbasic>do

 print "SPAM"

loop</lang>

Also <lang qbasic>for i = 1 to 10 step 0

 print "SPAM"

next i</lang>

With classic (minimal) BASIC, the standard way to make an infinite loop would be:

10 PRINT "SPAM"
20 GOTO 10

Batch File

Using goto: <lang dos>@echo off

loop

echo SPAM goto loop</lang> Another variant which uses Windows NT's for statement:

Works with: Windows NT version 4 or later

<lang dos>for /l %%x in (1,0,2) do @echo SPAM</lang> This essentially is a counted loop which starts at 1, increments by 0 and stops when the counter reaches 2.

Befunge

Because the 2-D code space is toroidal, all loops are infinite unless explicitly stopped with @. <lang befunge>55+"MAPS",,,,,</lang>

Brainf***

<lang bf>++++++++++[->++++++>++++++++>+<<<]>+++++> [+++.---.<.>---.+++>.<]</lang>

C

<lang c>while(1) puts("SPAM\n");</lang> or <lang c> for(;;) puts("SPAM\n");</lang> or <lang c>do { puts("SPAM\n"); } while(1);</lang>

C++

Translation of: C

<lang cpp>while (true)

 std::cout << "SPAM" << std::endl;</lang>

or <lang cpp>for (;;)

 std::cout << "SPAM" << std::endl;</lang>

or <lang cpp>do

 std::cout << "SPAM" << std::endl;

while (true);</lang>

C#

<lang csharp>while (true) {

   Console.WriteLine("SPAM");

}</lang>

ColdFusion

This will result in a JRun Servlet Error and heap dump.

With tags: <lang cfm><cfloop condition = "true NEQ false">

 SPAM

</cfloop></lang> With script: <lang cfm><cfscript>

 while( true != false )
 {
   writeOutput( "SPAM" );
 }

</cfscript></lang>

Clojure

<lang lisp>(loop [] (println "SPAM") (recur))</lang>

Common Lisp

<lang lisp>(loop (write-line "SPAM"))</lang>

D

<lang d>while(true) writefln("SPAM") ;</lang> <lang d>for(;;) writefln("SPAM") ;</lang> <lang d>l: writefln("SPAM"); goto l;</lang>

E

<lang e>while (true) {

   println("SPAM")

}</lang>

<lang e>def f() {

   println("SPAM")
   f <- ()

} f <- ()</lang>

The difference between these is that in the second, other activities can be interleaved with the loop; in the first, no other processing will occur in this vat.

Erlang

<lang erlang>-module (main). -export ([main/1]).

main(Any) ->

 io:fwrite("SPAM~n",[]),
 main(Any)</lang>

F#

<lang fsharp> while true do

   printfn "SPAM"

done

let rec forever () : unit =

   printfn "SPAM" ; forever ()

</lang>

Factor

<lang factor>: spam ( -- ) "SPAM" print spam ;</lang> <lang factor>: spam ( -- ) [ "SPAM" print t ] loop ;</lang>

FALSE

<lang false>[1]["SPAM "]#</lang>

Forth

<lang forth>: email begin ." SPAM" cr again ;</lang>

Fortran

Works with: Fortran version 90 and later

<lang fortran>DO

 WRITE(*,*) "SPAM"

END DO</lang> Although deprecated GOTO is still available <lang fortran>10 WRITE(*,*) "SPAM"

  GOTO 10</lang>

Go

<lang go>package main import "fmt" func main() { for { fmt.Printf("SPAM\n") } }</lang>

Groovy

<lang groovy>while (true) {

println 'SPAM'

}</lang>

Haskell

<lang haskell>forever (putStrLn "SPAM")</lang>

HicEst

<lang hicest>DO i = 1, 1E20 ! for i with 16 or more digits: i == i + 1 == loop infinite

   WRITE() "SPAM"

ENDDO</lang>

Icon and Unicon

Icon

There are several ways to write infinite loops in Icon. The most straightforward would be with repeat.

<lang icon>procedure main()

  repeat write("SPAM")

end</lang>

Alternately one could use one of these: <lang icon>until &fail do write("SPAM") # always fails, needs succeed to break ... while write("SPAM") # always succeeds, needs failure to break ... every write(|"SPAM") # generator always succeeds, needs failure to break ... while write(|"SPAM") # this is a common mistake that results in an endless loop ... while write(1 to 5) # a clearer version of the same mistake that generates endless 1's</lang>

Unicon

This Icon solution works in Unicon.

IDL

<lang IDL>while 1 do print,'SPAM'</lang>

Io

<lang io>loop("SPAM" println)</lang>

J

<lang j>(-[smoutput bind 'SPAM')^:_(1)</lang>

Alternatively,

<lang j>smoutput bind 'SPAM'^:1e99 </lang>

This second implementation relies on numeric inaccuracies in IEEE floating point notation. For example, 1+1e98 is exactly equal to 1e98. That said, 1e99 iterations would still be significantly longer than the practical life of any machine anyone would care to dedicate to this task.

Java

<lang java>while(true){

  System.out.println("SPAM");

}</lang>

<lang java>for(;;){

  System.out.println("SPAM");

}</lang>

JavaScript

<lang javascript>for (;;) print("SPAM"); while (true) print("SPAM");</lang>

Joy

<lang joy>DEFINE loop == [1] swap while.

["SPAM\n" putchars] loop.</lang>

Lisaac

The "lisaac" compiler apparently doesn't like infinite loops. Using a static slot (variable) seems to be the only way to get away with "Recursivity without end (call_slot)." error. <lang Lisaac>- i : INTEGER; i := 1; { i = 1 }.while_do {

 "SPAM\n".print;

};</lang>

<lang logo>forever [print "SPAM]</lang>

Lua

<lang lua> while 1 do

 print("SPAM")

end </lang>

M4

<lang M4>define(`spam',`SPAM spam') spam</lang>

Make

<lang make>spam:

  @echo SPAM
  $(MAKE)</lang>

Mathematica

<lang mathematica>While[True,

Print@"SPAM";
]</lang>

MAXScript

<lang maxscript>while true do print "SPAM\n"</lang>

Metafont

<lang metafont>forever: message "SPAM"; endfor end</lang>

Modula-3

<lang modula3>LOOP

 IO.Put("SPAM\n");

END;</lang>

MOO

<lang moo>while (1)

 player:tell("SPAM");

endwhile</lang>

MUMPS

<lang MUMPS>

FOR  WRITE "SPAM",!

</lang>

Objeck

<lang objeck> while(true) {

 "SPAM"->PrintLine();

}; </lang>

OCaml

<lang ocaml>while true do

 print_endline "SPAM"

done</lang>

or

<lang ocaml>let rec inf_loop() =

 print_endline "SPAM";
 inf_loop()

in inf_loop()</lang>

Seen like this it looks like the "too much functional" danger when a "while" loop looks far simpler, but the functional loop may be useful to provide data to the next loop without using mutable variable.

Octave

<lang octave>while(1)

 disp("SPAM")

endwhile</lang>

Oz

<lang oz>for do

  {Show 'SPAM'}

end</lang>

Pascal

<lang pascal>while true do

 writeln('SPAM');</lang>

Alternatively: <lang pascal>repeat

 writeln('SPAM')

until false;</lang>

Perl

<lang perl>print "SPAM\n" while 1;</lang>

Perl 6

Works with: Rakudo Star version 2010.08

<lang perl6>loop {

   say 'SPAM';

}</lang> In addition, there are various ways of writing lazy, infinite lists in Perl 6: <lang perl6>print "SPAM\n" xx *; # repetition operator print "SPAM\n", ~* ... *; # sequence operator map {say "SPAM"}, ^Inf; # upto operator</lang>

PHP

<lang php>while(1)

   echo "SPAM\n";</lang>

PicoLisp

<lang PicoLisp>(loop (prinl "SPAM"))</lang>

Pike

<lang pike>int main(){

  while(1) write("SPAM\n");

}</lang>

PL/I

<lang PL/I> do forever;

  put list ('SPAM'); put skip;

end; </lang>

Pop11

<lang pop11>while true do

   printf('SPAM', '%p\n');

endwhile;</lang>

PostScript

<lang postscript>{}loop</lang>

PowerShell

<lang powershell>for () {

   "SPAM"

}</lang>

Prolog

<lang prolog>repeat, write('SPAM'), nl, fail.</lang>

PureBasic

Repeat/Forever

<lang PureBasic>Repeat

 PrintN("SPAM")

ForEver</lang>

Goto

<lang PureBasic>PrintIt: PrintN("SPAM") Goto PrintIt</lang>

Python

<lang python>while 1:

  print "SPAM"</lang>

Note: one can also use: "True" or any other non-false value. In Python the following values are false: 0, "" (empty string), (,) and {} and [] (empty tuples, dictionaries or lists), None (the special object), and the False object. Any non-empty collection or string or non-zero numeric value is considered "True". However, according to Python Wiki, for Python versions 2.3+ this variant is optimized by the interpreter and thus is the fastest.

R

Note that the default R Gui buffers outputs before pushing them to the screen. To see this run either run in terminal mode, right click on the GUI window and deselect "Buffered Output" prior to execution, or add a call to flush.console() in the loop.

<lang R>repeat print("SPAM")</lang>

REBOL

<lang REBOL>forever [print "SPAM"]</lang>


REXX

<lang rexx>do forever

 say "SPAM"

end</lang>

Ruby

<lang ruby>loop do

  puts "SPAM"

end</lang>

Sather

<lang sather>class MAIN is

 main is
   loop 
     #OUT + "Spam\n"; 
   end;
 end;

end;</lang>

Scala

<lang scala>while (true)

 println("SPAM")</lang>

Scheme

<lang scheme>(do ()

   (#f)
   (display "SPAM")
   (newline))</lang>

Slate

<lang slate>[inform: 'SPAM'] loop</lang>

Smalltalk

<lang smalltalk>[ true ] whileTrue: [ 'SPAM' displayNl ]</lang>

SNOBOL4

<lang snobol>loop output = "SPAM" :(loop) end</lang>

SNUSP

<lang snusp>@\>@\>@\>@\>++++++++++===!/ < < < < \

|  |  |  \M=@@@@+@+++++# \.>.>.>.>./
|  |  \A=@@+@@@@+++#
|  \P=@@+@@+@@+++#
\S=@@+@+@@@+++#</lang>

Standard ML

<lang sml>while true do

 print "SPAM\n";</lang>

or

<lang sml>let

 fun inf_loop () = (
   print "SPAM\n";
   inf_loop ()
 )

in

 inf_loop ()

end</lang>

Seen like this it looks like the "too much functional" danger when a "while" loop looks far simpler, but the functional loop may be useful to provide data to the next loop without using mutable variable.

SystemVerilog

<lang SystemVerilog>program main;

 initial forever $display("SPAM");

endprogram </lang>

Transact-SQL

<lang sql>WHILE 1=1 BEGIN

PRINT "SPAM"

END</lang>

Tcl

<lang tcl>while true {

   puts SPAM

}

  1. or

for {} 1 {} {

   puts SPAM

}</lang>

TI-83 BASIC

There are a few ways to achieve this in TI-83 BASIC

<lang ti83b>

 :Goto 1
 :Lbl 1
 :Disp "SPAM"
 :Goto 1

</lang>

Another way is by using a While loop

<lang ti83b>

 :1→A
 :While A = 1
 :Disp "SPAM"

</lang>

TI-89 BASIC

<lang ti89b>Loop

 Disp "SPAM"

EndLoop</lang>

Trith

<lang trith>["SPAM" print] loop</lang>

UNIX Shell

Works with: Bourne Shell
Works with: Korn Shell
Works with: Almquist SHell
Works with: Bourne Again SHell
Works with: Z Shell

<lang bash>while :; do echo SPAM; done</lang>

UnixPipes

<lang bash> yes SPAM</lang>

Unlambda

<lang unlambda> ``ci``s``s`kr``s``s``s``s`k.S`k.P`k.A`k.Mii</lang>

V

<lang v>true [

  'SPAM' puts

] while</lang>

Vedit macro language

<lang vedit>while (1) {

   Message("Spam\n")

}</lang> or: <lang vedit>do {

   Message("Spam\n")

} while (1)</lang> or: <lang vedit>for (;1;) {

   Message("Spam\n")

}</lang> "Nearly infinite" loop can be done by using constant ALL (=1073741824) as repeat count: <lang vedit>Repeat (ALL) {

   Message("Spam\n")

}</lang>

Visual Basic

<lang vb>Do

   Debug.Print("SPAM")

Loop</lang>

Visual Basic .NET

Platform: .NET

Works with: Visual Basic .NET version 9.0+

<lang vbnet>Do

   Console.WriteLine("SPAM")

Loop</lang>

X86 Assembly

Works with: NASM version Linux

<lang asm> section .text global _start

_start: mov edx, len mov ecx, msg mov ebx, 1 mov eax, 4 int 0x80 jmp _start

section .data msg db "SPAM",0xa len equ $-msg </lang>