Re: Unnecessary Boolean Warning
Re: Unnecessary Boolean Warning
- Subject: Re: Unnecessary Boolean Warning
- From: Sander Stoks <email@hidden>
- Date: Thu, 04 Aug 2011 09:55:58 +0200
>> One important difference for instance is that if you write if (a() &
>> b()), both a() and b() will always be executed, while if you write if
>> (a() && b()), b() will be executed only if a() is true.
>
>
> The C language doesn't make any guarantees about that. While this
> optimisation is to be expected, the order of execution (left to right)
> and the optimisation (b not executed) is implementation dependent.
>
> This is a classic question for coding job interviews.
As has been pointed out, it most certainly does. This is important
because it allows you to write stuff like
if (index < maxIndex && isValid(array[index]))
...
In languages which don't guarantee short-circuiting, the array could be
indexed out-of-bounds.
On a related note, somebody said he would be less confused if C didn't
have "two different kind of booleans". In fact, it has none at all. It
is part of the idiom that you should read "if(a)" as "if a is non-zero"
and not as "if a is true".
Regards,
Sander
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