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.TH "al_fixsub" "3alleg5" "" "Allegro reference manual" ""
.hy
.SH NAME
.PP
al_fixsub - Allegro 5 API
.SH SYNOPSIS
.IP
.nf
\f[C]
#include <allegro5/allegro.h>

al_fixed al_fixsub(al_fixed x, al_fixed y);
\f[R]
.fi
.SH DESCRIPTION
.PP
Although fixed point numbers can be subtracted with the normal
\f[C]-\f[R] integer operator, that doesn\[cq]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\[cq]s errno and clamp the result, rather than just
letting it wrap.
.PP
Example:
.IP
.nf
\f[C]
al_fixed result;

/* This will put 4965 into \[ga]result\[aq]. */
result = al_fixsub(al_itofix(5000), al_itofix(35));

/* Sets errno and puts -32768 into \[ga]result\[aq]. */
result = al_fixsub(al_itofix(-31000), al_itofix(3000));
assert(!al_get_errno()); /* This will fail. */
\f[R]
.fi
.SH RETURN VALUE
.PP
Returns the clamped result of subtracting \f[C]y\f[R] from \f[C]x\f[R],
setting Allegro\[cq]s errno to ERANGE if there was an overflow.
.SH SEE ALSO
.PP
al_fixadd(3alleg5), al_fixmul(3alleg5), al_fixdiv(3alleg5),
al_get_errno(3alleg5).