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.TH "al_fixatan2" "3" "" "Allegro reference manual"
.SH NAME
al_fixatan2 \- Allegro 5 API
.SH SYNOPSIS
.IP
.EX
#include \f[B]<allegro5/allegro.h>\f[R]

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

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

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

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