4 ms·

Why do people write while(1) instead of for(;;)? Are you saying that "while(1)" is superior in some way? Why? I prefer "for(;;)" because it is explicitly defin

by pslam 14y ago

Why do people write while(1) instead of for(;;)? Are you saying that "while(1)" is superior in some way? Why? I prefer "for(;;)" because it is explicitly defined as an infinite loop, but "while(1)" needs an implicit cast of "1" to "true", and even then there's an implicit test for "true".

sp332 14y ago
You could just say while(true). And I'm not sure that the test for true is implicit, since that is what while() explicitly does.
- zanny 14y ago
  C doesn't have true / false as language constants, only as override-able macros. The good thing is modern compilers can evaluate a loop and if the break condition is constant it can just do an infinite loop without checking.
barbs 14y ago
I guess it's just personal preference. "for(;;)" looks really messy to me, and doesn't seem obvious that it signifies an infinite loop. I think that even the standard format for for loops (for (initialisation; condition; thing done at end of loop)) is quite unintuitive, and I have to think a bit to remember what each part does if one of them is omitted. It's also the only place I can think of where semicolons aren't expected at the end of a line (conventionally). I don't find a problem implicitly casting "1" to "true", I sort of do this automatically after programming in C for a while. Obviously if I were using java or something, I'd use "while(true)". Basically, I don't have to think much to know that it's an infinite loop :)
wollw 14y ago
True and false are actually defined as 1 and 0 respectively. I don't have a copy of the standard but this specifies true and false as macros. http://pubs.opengroup.org/onlinepubs/007904975/basedefs/stdbool.h.html http://pubs.opengroup.org/onlinepubs/007904975/basedefs/stdb... Edit: Of course I'm talking about C here. Also, I prefer for(;;) because it's an easy to recognize idiom that means "infinite loop."
tsahyt 14y ago
There's no casting involved in while(1). 1 is "true" in C, in fact, any integer != 0 is "true". I just did a quick check and gcc -S produces the same ASM output for both of them, which doesn't include any comparisons whatsoever, just a jmp. So both of them are really compiled to an actual infinite loop.

by pslam 14y ago

sp332 14y ago

You could just say while(true). And I'm not sure that the test for true is implicit, since that is what while() explicitly does.

zanny 14y ago
C doesn't have true / false as language constants, only as override-able macros. The good thing is modern compilers can evaluate a loop and if the break condition is constant it can just do an infinite loop without checking.

barbs 14y ago

I guess it's just personal preference. "for(;;)" looks really messy to me, and doesn't seem obvious that it signifies an infinite loop. I think that even the standard format for for loops (for (initialisation; condition; thing done at end of loop)) is quite unintuitive, and I have to think a bit to remember what each part does if one of them is omitted. It's also the only place I can think of where semicolons aren't expected at the end of a line (conventionally). I don't find a problem implicitly casting "1" to "true", I sort of do this automatically after programming in C for a while. Obviously if I were using java or something, I'd use "while(true)". Basically, I don't have to think much to know that it's an infinite loop :)

wollw 14y ago

True and false are actually defined as 1 and 0 respectively. I don't have a copy of the standard but this specifies true and false as macros. http://pubs.opengroup.org/onlinepubs/007904975/basedefs/stdbool.h.html http://pubs.opengroup.org/onlinepubs/007904975/basedefs/stdb... Edit: Of course I'm talking about C here. Also, I prefer for(;;) because it's an easy to recognize idiom that means "infinite loop."

tsahyt 14y ago

There's no casting involved in while(1). 1 is "true" in C, in fact, any integer != 0 is "true". I just did a quick check and gcc -S produces the same ASM output for both of them, which doesn't include any comparisons whatsoever, just a jmp. So both of them are really compiled to an actual infinite loop.