.TH "al_fixatan2(3alleg5) Allegro reference manual" "" "" "" ""
.SH NAME
.PP
al_fixatan2 \- Allegro 5 API
.SH SYNOPSIS
.IP
.nf
\f[C]
#include\ <allegro5/allegro.h>

al_fixed\ al_fixatan2(al_fixed\ y,\ al_fixed\ x)
\f[]
.fi
.SH DESCRIPTION
.PP
This is a fixed point version of the libc atan2() routine.
It computes the arc tangent of \f[C]y\ /\ x\f[], but the signs of both
arguments are used to determine the quadrant of the result, and
\f[C]x\f[] is permitted to be zero.
This function is useful to convert Cartesian coordinates to polar
coordinates.
.PP
Example:
.IP
.nf
\f[C]
\ \ \ \ al_fixed\ result;

\ \ \ \ /*\ Sets\ `result\[aq]\ to\ binary\ angle\ 64.\ */
\ \ \ \ result\ =\ al_fixatan2(al_itofix(1),\ 0);

\ \ \ \ /*\ Sets\ `result\[aq]\ to\ binary\ angle\ \-109.\ */
\ \ \ \ result\ =\ al_fixatan2(al_itofix(\-1),\ al_itofix(\-2));

\ \ \ \ /*\ Fails\ the\ assert.\ */
\ \ \ \ result\ =\ al_fixatan2(0,\ 0);
\ \ \ \ assert(!al_get_errno());
\f[]
.fi
.SH RETURN VALUE
.PP
Returns the arc tangent of \f[C]y\ /\ x\f[] in fixed point binary format
angle, from \-128 to 128.
If both \f[C]x\f[] and \f[C]y\f[] are zero, returns zero and sets
Allegro\[aq]s errno to EDOM.