al_fixsub(3)                                                      al_fixsub(3)

NAME
       al_fixsub - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              al_fixed al_fixsub(al_fixed x, al_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 Allegro's errno and clamp the result, rather than just letting it
       wrap.

       Example:


              al_fixed result;

              /* This will put 4965 into `result'. */
              result = al_fixsub(al_itofix(5000), al_itofix(35));

              /* Sets errno and puts -32768 into `result'. */
              result = al_fixsub(al_itofix(-31000), al_itofix(3000));
              assert(!al_get_errno()); /* This will fail. */


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

SEE ALSO
       al_fixadd(3), al_fixmul(3), al_fixdiv(3), al_get_errno(3).

Allegro reference manual                                          al_fixsub(3)