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.TH "al_fixatan2" "3alleg5" "" "Allegro reference manual" ""
.hy
.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[R]
.fi
.SH DESCRIPTION
.PP
This is a fixed point version of the libc atan2() routine.
It computes the arc tangent of \f[V]y / x\f[R], but the signs of both
arguments are used to determine the quadrant of the result, and
\f[V]x\f[R] 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 \[ga]result\[aq] to binary angle 64. */
result = al_fixatan2(al_itofix(1), 0);

/* Sets \[ga]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[R]
.fi
.SH RETURN VALUE
.PP
Returns the arc tangent of \f[V]y / x\f[R] in fixed point binary format
angle, from -128 to 128.
If both \f[V]x\f[R] and \f[V]y\f[R] are zero, returns zero and sets
Allegro\[cq]s errno to EDOM.