On 20011122 Stevie O wrote:
>At 12:35 PM 11/21/2001 +0000, Vincent Sweeney wrote:
>> > Bad code style. Bad name (sounds like 'module inc').
>> > I can't even tell from this define what the hell it is trying to do:
>> > x++ will return unchanged x, then we obtain (x mod y),
>> > then we store it into x... and why x++ then??!
>> > Alan, seems like you can help here...
>>
>>Go read up on C operator precedence. Unary ++ comes before %, so if we
>>rewrite the #define to make it more "readable" it would be #define
>>MODINC(x,y) (x = (x+1) % y)
>
>But x++ is postincrement though. That means the value of 'x' is inserted,
>and after the expression is evaluated, x is incremented. Right?
>
>If we were going to be semiobscure, wouldn't the correct code be
>
>#define MODINC(x,y) (x = ++x % y)
>
But the question is: Is this kind of code worth the discussion ? AFAIK,
gcc is enough smart to change *2 to <<1, so wouldn't it be smart to
detect a +1 and use and inc (and perhaps to detect that x is overwritten so it
can do the op in place).
So write it as
x = (x+1)%y
and make it readable.
-- J.A. Magallon # Let the source be with you... mailto:jamagallon@able.es Mandrake Linux release 8.2 (Cooker) for i586 Linux werewolf 2.4.15-pre9 #1 SMP Thu Nov 22 16:16:54 CET 2001 i686 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Nov 23 2001 - 21:00:31 EST