.\" Generated by the Allegro makedoc utility
.TH fixsub 3alleg4 "version 4.4.2" "Allegro" "Allegro manual"
.SH NAME
fixsub \- Safe function to subtract fixed point numbers clamping underflow. Allegro game programming library.\&
.SH SYNOPSIS
.B #include <allegro.h>

.sp
.B fixed fixsub(fixed x, fixed y);
.SH 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:

.nf
   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. */
.fi
.SH "RETURN VALUE"
Returns the clamped result of subtracting `y' from `x', setting `errno' to
ERANGE if there was an overflow.

.SH SEE ALSO
.BR fixadd (3alleg4),
.BR fixmul (3alleg4),
.BR fixdiv (3alleg4)