Rounding in C Preprocessor

I am defining some values in the preprocessor. e.g.

#defin开发者_运维技巧e a 1000
#define b 0.5*a

When I try to use b in a place where integer is needed I get an error. I don't want to cast b always in my code and do it once in the #define line, is that possible?

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Try this:

#define a 1000
#define b (a/2)

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#define b ((int)(a * 0.5))