fixsub - Man Page
Safe function to subtract fixed point numbers clamping underflow. Allegro game programming library.
Synopsis
#include <allegro.h>
fixed fixsub(fixed x, fixed y);
Description
Although fixed point numbers can be subtracted with the normal '-' integer operator, that doesn't provide any protection against overflow. If overflow is a problem, you should use this function instead. It is slower than using integer operators, but if an overflow occurs it will set `errno' and clamp the result, rather than just letting it wrap. Example:
fixed result; /* This will put 4965 into `result'. */ result = fixsub(itofix(5000), itofix(35)); /* Sets `errno' and puts -32768 into `result'. */ result = fixsub(itofix(-31000), itofix(3000)); ASSERT(!errno); /* This will fail. */
Return Value
Returns the clamped result of subtracting `y' from `x', setting `errno' to ERANGE if there was an overflow.
See Also
Referenced By
fixadd(3), fixdiv(3), fixmul(3).
version 4.4.3 Allegro manual