Messages in this thread | | | Date | Wed, 21 Nov 2001 23:24:02 -0500 | From | Stevie O <> | Subject | Re: [BUG] Bad #define, nonportable C, missing {} |
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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)
Btw, to the original guy: this loops 'x' around between 0 and (y-1) -- i.e., if y=5, and x=0, successive "calls" to this #define would do
MODINC(x,y); // x=1 MODINC(x,y); // x=2 MODINC(x,y); // x=3 MODINC(x,y); // x=4 MODINC(x,y); // x=0 MODINC(x,y); // x=1 MODINC(x,y); // x=2 MODINC(x,y); // x=3 ...
-- Stevie-O
Real programmers use COPY CON PROGRAM.EXE
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