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Challenge: Write a program that never stops

Florian Rohrer on October 19, 2017

Write an endless loop, write some confusing gotos... The rules are simple: Write a program that never stops. Language: Any. Try to keep it short a...

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Ryan Palo • Oct 19 '17

Ruby:

loop {:D}

Florian Rohrer • Oct 19 '17

This gotta be the happiest loop, I've ever seen.

David Muckle • Oct 19 '17 • Edited

:(){:|:&};:

10 PRINT "HELLO!"
20 GOTO 10

Always gotta have the classics.

Perry Ahern • Oct 19 '17 • Edited

Ah, BASIC with manually typed line numbers and GOTO... If only the screenshot were monochromatic green or amber it would be truly classic.

David Muckle • Oct 19 '17

I can do that if you'd like... dev.to/dvdmuckle/hooking-up-a-vt42... :)

Perry Ahern • Oct 19 '17

That'd be cool to see, but it'd never replace my memories of flickering Commodore PET screens from days of yore. Cool write up though, saving that to read later.

Jessy • Oct 19 '17

function a(){
  a();
}

a();

Endless recursivity!

Halt! 6 kere 9? • Oct 19 '17

This will crash once the stack is full but nice try. :)

Arne Mertz • Oct 19 '17

Use a language that allows optimization of tail recursion then ¯_(ツ)_/¯

Phoebe Goldman • Oct 20 '17

Us cool kids with our tail recursion could write in, for example, Common Lisp:

(defun loop-for-ever ()
  (loop-for-ever))
(loop-for-ever)

Jessy • Oct 19 '17

Hahaha yeah it totally did crash Chrome when I tried it. I wanted to just post

while(true){}

but that's a little boring.

Halt! 6 kere 9? • Oct 19 '17

Definitely classic but lacks the humor :)

Luciano Quercia • Oct 19 '17

var f float32
for f = 0; int(f) < 16777217; f++ {
    fmt.Println("Hello!")
}

Kajigga • Oct 19 '17

python

while 1:1

never-ending song

from itertools import cycle
import time
list = ['This is the song that never ends',
    'It just goes on and on my friends',
    'Some people started singing it, not knowing what it was',
    'And they\'ll continue singing it forever just because...']

for line in cycle(list):
    print(line)
    time.sleep(.25)

non-stop random numbers

from random import randint
def infinite_random():
    while True:
        yield randint(1,1000000000)

for x in infinite_random():
    print(x)

lots of random user information

import requests
def get_users():
    while True:
        yield requests.get('https://randomuser.me/api/').json()['results'][0]

for user in get_users():
    print('{0[name][first]} {0[name][last]} - born {0[dob]}'.format(user))

Peter Kim Frank • Oct 20 '17

The "never-ending song" is classic. 😂

Miff • Oct 19 '17

Brainfuck, I guess.

+[]

Arne Mertz • Oct 19 '17 • Edited

C++

#define ever ;;
int main() {
  for(ever);
}

int main() {
    for (unsigned i = 341; i > 0; --i) {
        printf("%u\n", i--);
    }
}

int main() {
    float f = 1.0f;
    while (f < 16777218.2f) {
        printf("%f\n", f);
        f += 1;
    }
}

assembler

main:
.L2
  jmp .L2

int main(void) {
    int b=0, a[] = {0,1};
    while (b != (!b)[a]) {
        printf("%i\n", b=!a[b]);
    }
}

int main(void) {
  https://dev.to
  goto https;
}

Florian Rohrer • Oct 19 '17

I really like the last one. Defining a label to a comment - nice :D

Halt! 6 kere 9? • Oct 19 '17

This is far the best 👍

raja sudhan • Oct 20 '17

very nice friend!!

Valentin Baca • Oct 19 '17 • Edited

Javascript (empty statement evaluates to true so is effectively while(true)): for(;;);

Super-Evil Javascript DON'T RUN THIS LOL: for(;;)alert();

Python: while 1:0

Shell: yes
Funny story about yes is that in Unix it's actually just a blank file, which AT&T has the copywrite for o.0

Parth Parikh • Oct 19 '17

Welcome to Verilog.

module tb();
    always $display("You think I will stop? Think again!");
endmodule;

Karn Saheb • Oct 19 '17

My god, this brings back memories that I've been trying to compartmentalize. :'(

unused • Oct 21 '17 • Edited

Was missing a uninterruptible one

#include <signal.h>
void main(void) {
  sigset_t stop;
  sigemptyset (&stop);
  sigaddset(&stop, SIGINT);
  sigaddset(&stop, SIGTSTP);
  sigprocmask(SIG_BLOCK, &stop, NULL);

  for(;;);
}

Patrik • Oct 20 '17

Only to make people hate me...

HTML

<marquee>You spin my head right round, right round...</marquee>

Rodrigo Martins • Oct 22 '17

Python

valuе = 0
while valuе < 1:
    value = valuе + 1

Python

i = 0
j = 10
while not i is j:
    i += 1

print("i is j: " + str(i is j))

j = 257
while not i is j:
    i += 1

print("unreachable")

eminemence • Oct 19 '17 • Edited

Shell command :
yes

Daniel Escoz • Oct 19 '17 • Edited

Javascript (ES6):

const zero = () => Promise.resolve(0).then(zero);
zero().then(result => console.log('this does not print a zero:', result));

Technically ends because .then run on the next tick, but it permanently blocks the JS event loop (I think).

(It might eat your RAM)

Florian Rohrer • Oct 19 '17 • Edited

// 1
int i = 0;
while(i < 10)
{
    if(i = 5)
        printf("i is 5!");
    i++;
}
// 2
for(int i = 0; i < 10; i++);
{
    printf("hello");
}
// 3
for(int i = 1; i < 11, i++;)
{
    printf("hello");
}

Lucio Rossi • Oct 20 '17

This is not a program in the strict sense and surely it will never run forever, but still it's a lot of fun

<IfModule mod_ssl.c>
<VirtualHost *:443>
   RewriteEngine on
   RewriteRule ^ https://%{SERVER_NAME}/fun%{REQUEST_URI} [END,NE,R=permanent]
</VirtualHost>
</IfModule>

Dan Suzuki • Oct 19 '17

Scala

@tailrec 
final def diamond(b: Boolean): Boolean = 
   if(b) diamond(b) 
   else b

Erry Kostala • Dec 15 '17

#!/usr/bin/env perl

$SIG{INT} = 'IGNORE';

while ( 1 ) {
  print "stop me if you can\n";
  sleep 1;
}

# Pretty standard but I went a bit further and made it ignore CTRL-C as well, so you have to `kill -9` it :)

Carsten • Oct 21 '17

Haskell

go = 1:go

Craig McIlwrath • Aug 22 '19

Isn't this program fine? It never forces evaluation of go so the program immediately exits.

Carsten • Aug 23 '19 • Edited

of course I assumed you would evaluate the expression (for example in the repl)

you are technical right but it's a bit like commenting to all the others and saying "it's fine as long as you don't run it" ;)

just assume a

main = print go

there if you like

Alexandre Plt • Nov 10 '17 • Edited

C++

#include <iostream>
int main(int argc, char* argv)
{
    std::cout << "argc is " << argc << std::endl;
    std::cout << main(argc, argv);
    return main(1, {'H', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', '\0'});
}

C++ (even though the syntax highlithing is set to python)

#include <my_awesome_events_manager_lib>
using namespace my_awesome_events_manager_lib;
int main(void)
{
    auto playing = true;
    while (playing)
    {
        // handle events /!\
        if (getEvent()->type == QUIT) playing = !playing;
    }
    return 0x0;
}

Programming Liftoff • Oct 26 '17

int main() {
  int x = 1;
  while(x>0);
  {
    x--;
  }
}

Meghan (she/her) • Oct 19 '17

Javascript

setInterval(function() {}, 1);

Valentin Baca • Nov 10 '17 • Edited

The original post was tagged with javascript and dev.to has a bias toward javascript which is why it was tagged with that.

What language would you have picked? Because most languages do not have empty statements evaluate to true, so the block would have had to be for(;1;); which is not as neat IMO

Daniel Albuschat • Nov 10 '17

Andreas Jakof • Oct 24 '19

class Program
{
   public static IEnumerable<string> HelloWorld()
   {
      while(true) yield return „Hello World“;
   }
   public static void Main(string[] args)
   {
      foreach (string  s in HelloWorld())
      {
         Console.WriteLine(s);
         Thread.Sleep(1000);
      }
   }
}

Phoebe Goldman • Oct 20 '17

Rust:

fn main() {
    loop {
    }
}

Or, for a slightly more involved example:

use std::num::Wrapping;
use std::iter::Iterator;

struct Fibs {
    n: Wrapping<usize>,
    n_minus_one: Wrapping<usize>,
}

impl Fibs {
    fn new() -> Self {
        Fibs {
            n: Wrapping(1),
            n_minus_one: Wrapping(0),
        }
    }
}

impl Iterator for Fibs {
    type Item = Wrapping<usize>;
    fn next(&mut self) -> Option<Self::Item> {
        let n_plus_one = self.n + self.n_minus_one;
        self.n_minus_one = self.n;
        self.n = n_plus_one;
        Some(n_plus_one)
    }
}

fn main() {
    let mut fibs = Fibs::new();
    while let Some(n) = fibs.next() {
        println!("{}", n);
    }
}

Ignacio Losiggio • Oct 19 '17 • Edited

A classical example :P

(λx.x x)(λx.x x)

Or in ES2015

(a=>a(a))(a=>a(a))

Ayush • Oct 20 '17 • Edited

for (;;cout<<"forever");

#benaryorg • Nov 10 '17 • Edited

Using C and TCO:


#define foo(x) _foo((x),1,0)

int _foo(int to,int cur,int acc)
{
  if((cur = 0) || (to = cur))
  {
    return acc;
  }
  return _foo(to,cur+1,acc+cur);
}

int main(void)
{
  return foo(10);
}

Nigel Kirby • Oct 19 '17

2 JS classics

let a = 1
while(a !== '1')
    console.log('sup')

let a = 0.1 * 0.2
while(a !== .02)
    console.log('sup')

Carlos Gortaris • Oct 23 '17

while(fork());

This ends when enough sysadmins get annoyed. We used to call it "fork bomb" at the University systems.

Blaž Šelih • Oct 20 '17

Z80 assembly

loop: JR loop

compiles down to two bytes: 18 FD

Frederik 👨‍💻➡️🌐 Creemers • Oct 20 '17

his technically doesn't run forever, but takes longer than you'd expect:

Python:

import re

exp = re.compile("a(b|c+)*d")
exp.match("a" + "c"*100)

Florian Rohrer • Oct 20 '17

haha, reminds me of:
stackstatus.net/post/147710624694/...

Jens • Oct 20 '17 • Edited

for(int i = 0; i < 10; i++)
{
  i--;
}

Jp1337 • Oct 20 '17

int main(){
    uint8_t i=0;
    while( ++i > i++ ? i-- : --i );
}

Eugeniu T. • Nov 10 '17 • Edited

Elixir:

def infinite do
    infinite
end

Gary Marriott • Oct 19 '17 • Edited

Erlang:
loop() -> do:someVitalTask(), loop().

Gökhan Kurt • Dec 15 '17

_=        '._.'   // Dude WTF

for       (;_;)   // Stop that pls

          _=_=_   // IDC LOL

Filip Bielejec • Oct 19 '17

Clojure

(while true (do))

(Behold the beauty of LISP :) )

Thomas Rigby • Nov 10 '17

while (true) {
  console.log(!true)
}

Pablo • Nov 10 '17

2 bytes. Language: MATL

Paula • Oct 19 '17

This post is so dangerous oh my god

tonnoz • Oct 21 '17 • Edited

Java8

The matrix has you:

Stream.iterate("", i -> i = Character
    .toString((char) new Random().nextInt(255)))
.forEach(i-> System.out.print(i));

tonnoz • Oct 21 '17

Stream.iterate('a', i-> i= (char)new Random().nextInt(255)).forEach(i-> System.out.print(i));

Johan • Oct 19 '17

Ruby

loop do
  puts 'trololo'
end

michie1 • Oct 19 '17

while(1){}

sur0g • Oct 20 '17 • Edited

#python
for person in dumb_people_around_me:
 print('Yay!')

Mark Ciccarello • Oct 20 '17

int main()
{
   int i = 0;
   while(i < 10) {
      println("Hello world");
      i = i++;
   }

}

Bharath • Oct 21 '17 • Edited

Swift :

repeat { print("Hello") } while(true)

Kenan • Oct 20 '17

while True:
print('something')

Oliver Weiler • Oct 24 '17

bash (probably sh too)

while :; do :; done

Gustavo • Oct 20 '17

Windows Programming:
:1
start
goto 1

indra452 • Oct 20 '17

while (true) {}

crhodes • Oct 28 '17

Oooh! This is fun!

Python:

ImCrazy4You = True

while (ImCrazy4You):
print "I will always stalk you, forever!";

Daan Wilmer • Nov 5 '17

On linux bash:

cat /dev/urandom > /dev/null

Andrew T Johnson • Oct 26 '17

The Earth was designed to run forever, until the Vogons needed to put in a hyperspace expressway. 😂

bruno jennrich • Oct 20 '17

for(;;);

crhodes • Nov 9 '17

Infinite insult in C

int YourIQ = 0;
while (YourIQ < 1)
{
    printf("You're stupid! ");

}

bruno jennrich • Oct 20 '17

while(true);

crhodes • Oct 28 '17 • Edited

Oooh! This is fun!

Python:
ImCrazy4You = True
while (ImCrazy4You):
print "I will always be watching you, forever!";

fzngagan • Oct 20 '17

void main(){
main();
}