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Is “for(;;)” faster than “while (TRUE)”? If not, why do people use it?
I was wondering what is the difference between for(;;) and while(1) when both perform same function? Will there be any difference of speed of compilation
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6How can you close a __C++ best-practice__ question pointing to __C# best-practice__ answers? Sorry, but this is absurd. Voted to re-open. – sbi Dec 04 '10 at 10:53
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will there be any difference in the compilation speed!!generally programmers are said to use while rather than for – abhinav Dec 04 '10 at 11:16
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@sbi: I think the confusion results from the answers being virtually equivalent between the two questions. But I agree, this *is* a distinctly different question. – Cody Gray - on strike Dec 04 '10 at 11:41
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1If anything, this is a more appropriate duplicate: http://stackoverflow.com/questions/2611246/is-for-faster-than-while-true-if-not-why-do-people-use-it – Cody Gray - on strike Dec 04 '10 at 11:42
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@Cody: It is indeed. Is it an _exact_ duplicate? Shall we close this one pointing to it? (And: Even if the answers to best-practice syntax questions are virtually equivalent between languages, _best practice syntax_ IMO still warrants language-specific questions. And my answer doesn't even apply to C#, since it doesn't have as many compilers as C++ has.) – sbi Dec 04 '10 at 11:51
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The difference with these is that many compilers will warn about while(true) ("constant expression used as loop expression"), while none I know of warn about for(;;).
They should generate the same code, though.
sbi
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...which seems like a big plus for `for(;;)`, since no-one really writes either `while(true)` or `for(;;)` by accident. – Stuart Golodetz Dec 04 '10 at 11:56
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I guess yup. Sorry, prob didn't need to stick my oar in there... – Stuart Golodetz Dec 04 '10 at 12:10
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With for, you can do this:
#define ever (; ;) // note the two happy faces? ;)
for ever { ... } // endless loop
Which is not possible with while.
fredoverflow
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2+1 for creativity, yes. However, you can write: #define forever (1) while forever {...} – Baltasarq Dec 04 '10 at 13:49
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Could one not `#define forever for(; ;)` and then `forever{ --age }`... – flcoder Feb 18 '18 at 13:02
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- Both will cause infinite loop unless
breakis called explicitly. - Personally I prefer while(1), it's more readable
Andreas Wong
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No difference. I prefer the latter.
Prasoon Saurav
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will there be any speed difference during the time of compilation..another thing saurav did u see my other quwstion the automatic gear shift i,m looking forward to u ans that question!! – abhinav Dec 04 '10 at 08:52
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@abhinav : No the machine code generate would most probably be same in both the cases. As far as I can see you have already accepted an answer to that question. – Prasoon Saurav Dec 04 '10 at 08:54
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@saurav i accepted the answer but i'm still looking forward to a different approach.. – abhinav Dec 04 '10 at 09:03
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@saurav can you plz tell me which book should i refer for c++ i'm doin engg 1st year and i don't have much idea bout the lang – abhinav Dec 04 '10 at 09:21
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No difference, unless you want to make use some kind counter later as below.
for (int i =0; i < 100; i++) {
// some code
}
fastcodejava
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Both are the same in C++. However, your post is tagged with c# and c++.
If you're using C#, you'll need to use while (true) {...}. Personally, I prefer the same in C++: numbers are used only when dealing with... well, numbers! When dealing with boolean values, true and false are used instead.
ClosureCowboy
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They both defines the exact same functional behavior and produce exactly the same IL code from C#.
VdesmedT
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I'm old-school, I still do the following:
#define TRUE 1
#define FALSE 0
while (TRUE) { /*--do something, mutley--* }
Joel
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Simon Catlin
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