DOKK / manpages / debian 11 / allegro4-doc / fixsub.3alleg4.en
fixsub(3alleg4) Allegro manual fixsub(3alleg4)

fixsub - Safe function to subtract fixed point numbers clamping underflow. Allegro game programming library.

#include <allegro.h>

fixed fixsub(fixed x, fixed y);

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. */

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

fixadd(3alleg4), fixmul(3alleg4), fixdiv(3alleg4)

version 4.4.3 Allegro