Infinite loops - top or bottom? [closed]

Question

In the spirit of questions like Do your loops test at the top or bottom?:

Which style do you use for an infinite loop, and why?

• while (true) { }
• do { } while (true);
• for (;;) { }
• label: ... goto label;

Yogini

Related question: https://mcmap.net/q/18819/-why-use-infinite-loops – Yogini

possible duplicate of Endless loop in C/C++ – Ashlan

It's popular in some circles to do #define ever ;; just so you can then do for(ever){ … }. – Householder

Answer 1

while(true) {}

It seems to convey the meaning of the loop most effectively.

Diegodiehard

Answer 2

for (;;)
{
    /* No warnings are generated about constant value in the loop conditional
       plus it is easy to change when you realize you do need limits */ 
}

Vicennial

Answer 3

#define forever for(;;)

forever {
    /*stuff*/
}

Theodolite

Answer 4

while(1)
{
//do it 
}

That's how I roll.

Fred

Answer 5

I like to use the for(;;) approach because the MSVC++ compiler complains about while loop approach:

void main()
{
  while(1) // test.cpp(5) : warning C4127: conditional expression is constant
  {
  }

  for(;;)
  {
  }
}

Meanwhile

I like that it complains - gives a cue that, yes, it is indeed an infinite loop. – Fred

Answer 6

I prefer while(1) or while(true) -- it's the clearest. do { } while(true) seems like needless obfuscation. Likewise, for(;;) can be confusing to people that have never seen it before, whereas while(true) is very intuitive. And there's absolutely no reason to do label: ... goto label;, it's just more confusing.

Whortleberry

'while (true)' could be confusing as 'for (;;)' if you think about it too long. Under what circumstances does the while exit? Maybe a '#define forever while(true)' would give us a more English keyword. – Parvenu

My thoughts exactly, Adam. for (;;) is cool in a dirty C kind of way, but I wouldn't bring it out in public. – Wendeline

Answer 7

I use for (;;) in C-style languages and while true in languages that don't support that construct.

I learned the for (;;) method in K&R and it has always felt like idiomatic C to me.

Ibnsina

Answer 8

Infinite tail-recursion ;)

It's somewhat compiler-dependant...

Embryologist

Only if you use a niche compiler. The most important ones do it as optimizations. – Strother

Answer 9

I usually use for(;;) { } which I always think of as "for-ever".

Some languages offer a repeat { } construct which will natively loop forever. I find the for(;;) { } construct visually the most similar to this because it is so different from the normal for() construct. This is an important attribute for an infinite loop that while(1) { } doesn't really have.

Teat

Which languages have a repeat keyword? – Mcdaniel

Dunno, but Perl 6 has loop { } for the same idea. – Musicianship

Icon, Logo and Rexx are the first that come to mind. There are others. – Teat

R has repeat { } too. – Fee

Answer 10

10 some l33t code
20 goto 10

Anorexia

Answer 11

Let the flaming begin...

If the loop is a true infinite loop (i.e. there is no break condition -- only an external event can terminate the thread's/process' execution), then I actually prefer the label and goto. Here's why:

First, the use of while, for, and do ... while, all imply that the loop might terminate. Even if the terminating condition is never achievable, the syntactical meaning of these constructs is that there is some termination condition.

Second, using a loop construct introduces an extra level of indentation. I hate indentation that's not necessary. It wastes valuable columnar real-estate.

Third, the only true infinite loop is the one that unconditionally jumps back to the beginning of the loop. Only goto fits that purpose exactly.

The truth is I don't really care that much about it. They all get the job done and most will result in the exact same assembly instructions anyway. However, the assembly that's generated will in all probability be an unconditional jump (if you're optimizer is worth a damn), which maps directly to which C construct, kids? That's right... your old friend goto.

Underprop

Answer 12

for(;;);

Filler text.

Coz

Answer 13

for (;;) is what I usually see.

Demeter

Answer 14

offtopic: if you think about what you are trying to express, you usually won't need an infinite loop.

Susann

Not necessarily. I've run across many cases where an infinite loop (with or without a break) is the cleanest way to express something. – Cockaigne

Ya, I have observed the same thing. I pop in an infinite loop, and morph the code to meet the unit test. Before I can blink, I see that it can be turned into a normal loop construct. – Vicennial

Answer 15

When writing code for myself I use for(;;). Other people tend to be confused by its syntax and so for code that other people must see/use, I use while(true).

Religiosity

If other people are confused by that syntax, they need to learn the programming language better. It's hard to imagine someone being caught off-guard by something in the core language syntax... – Musicianship

Answer 16

I now prefer the "for (;;)" idiom because it seems to 'stick out' more. I used to use the "while (true)" idiom because I thought it expressed intent better, but I've switched over because I think the "for (;;)" idiom is well known enough to adequately express intent as well as I believe it's better by being more visible.

Kind of like how Stroustrup made the new casts in C++ purposefully ugly - so they stick out.

Frig

Answer 17

I usually use while() {}, but after learning that for(;;) {} isn't some sort of crazy invalid syntax, I'll be sure to use the more unique option.

Differentiates infinite loops from actual conditionals, you see.

Kyat

Answer 18

Infinite loops are a bad idea, but in practice that doesn't always hold up.

I prefer while(1) { } but make sure something within the loop can cause it to break out.

Halmstad