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fixmul.3alleg

NAME

fixmul - Multiplies two fixed point values together. Allegro game programming library.

SYNOPSIS

#include <allegro.h>

fixed fixmul(fixed x, fixed y);

DESCRIPTION

A fixed point value can be multiplied or divided by an integer with the normal `*' and `/' operators. To multiply two fixed point values, though, you must use this function.

If an overflow occurs, `errno' will be set and the maximum possible value will be returned, but `errno' is not cleared if the operation is successful. This means that if you are going to test for overflow you should set `errno=0' before calling fixmul(). Example:

    fixed result;
    
    /* This will put 30000 into `result'. */
    result = fixmul(itofix(10), itofix(3000));
    /* But this overflows, and sets `errno'. */
    result = fixmul(itofix(100), itofix(3000));
    ASSERT(!errno);
 

RETURN VALUE

Returns the clamped result of multiplying `x' by `y', setting `errno' to ERANGE if there was an overflow.

SEE ALSO

fixadd(3alleg), fixsub(3alleg), fixdiv(3alleg), ex3buf(3alleg), excustom(3alleg), exfixed(3alleg), exspline(3alleg), exstars(3alleg), exupdate(3alleg)