Is "for(;;)" faster than "while (true)"? If not, why do people use it?
for (;;) {
//Something to be done repeatedly
}
I have seen this sort of thing used a lot, but I think it is rather strange...
Wouldn't it be much clearer to say while(true), or something along those lines?
I'm guessing that (as is the reason for many-a-programmer to resort to cryptic code) this is a tiny margin faster?
Why, and is it really worth it? If so, why not just define it this way:
#define while(true) for(;;)
See also: Which is faster: while(1) or while(2)?
- It's not faster.
- If you really care, compile with assembler output for your platform and look to see.
- It doesn't matter. This never matters. Write your infinite loops however you like.
I prefer for(;;) for two reasons.
One is that some compilers produce warnings on while(true) (something like "loop condition is constant"). Avoiding warnings is always a good thing to do.
Another is that I think for(;;) is clearer and more telling.
I want an infinite loop. It literally has no condition, it depends on nothing. I just want it to continue forever, until I do something to break out of it.
Whereas with while(true), well, what's true got to do with anything? I'm not interested in looping until true becomes false, which is what this form literally says (loop while true is true). I just want to loop.
And no, there is absolutely no performance difference.
Personally I use for (;;) because there aren't any numbers in it, it's just a keyword. I prefer it to while (true), while (1), while (42), while (!0) etc etc.
Because of Dennis Ritchie
I started using
for (;;)because that's the way Dennis Ritchie does it in K&R, and when learning a new language I always try to imitate the smart guys.This is idiomatic C/C++. It's probably better in the long run to get used to it if you plan on doing much in the C/C++ space.
Your
#definewon't work, since the thing being #define'd has to look like a C identifier.All modern compilers will generate the same code for the two constructs.