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.TH al_fixsub 3 "" "Allegro reference manual"
.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[]
.fi
.SH DESCRIPTION
.PP
Although fixed point numbers can be subtracted with the normal
\f[C]\-\f[] integer operator, that doesn\[aq]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\[aq]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\ `result\[aq].\ */
\ \ \ \ result\ =\ al_fixsub(al_itofix(5000),\ al_itofix(35));
\ \ \ \ /*\ Sets\ errno\ and\ puts\ \-32768\ into\ `result\[aq].\ */
\ \ \ \ result\ =\ al_fixsub(al_itofix(\-31000),\ al_itofix(3000));
\ \ \ \ assert(!al_get_errno());\ /*\ This\ will\ fail.\ */
\f[]
.fi
.SH RETURN VALUE
.PP
Returns the clamped result of subtracting \f[C]y\f[] from \f[C]x\f[],
setting Allegro\[aq]s errno to ERANGE if there was an overflow.
.SH SEE ALSO
.PP
al_fixadd(3), al_fixmul(3), al_fixdiv(3), al_get_errno(3).
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