min/max macros
Gerald Pfeifer
pfeifer@dbai.tuwien.ac.at
Thu Dec 11 13:43:00 GMT 1997
On Thu, 11 Dec 1997, Bill Ahlbrandt wrote:
> I "coded" my own and used them as follows:
>
> #define max(a,b) (((a) > (b)) ? (a) : (b))
> #define min(a,b) (((a) < (b)) ? (a) : (b))
That is a big no-no: Absolutely no performance benefits with any decent
compiler but nasty side effects.
> After discovering that max in particular was not yielding the desired
> results [...]
You didn't happen to use "max(i++,prev_max)" or similar, did you?
For that expands to
(((i++) > (prev_max)) ? (i++) : (prev_max))
which may increment i twice as an -- usually unintended -- side-effect.
Hope this helps,
Gerald
--
Gerald Pfeifer (Jerry) Vienna University of Technology
pfeifer@dbai.tuwien.ac.at http://www.dbai.tuwien.ac.at/~pfeifer/
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