---
name: "al_fixatan2"
section: "3"
platform: "linux"
package: "allegro"
version: "5.2.11.3-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/al_fixatan2"
---

# al\_fixatan2(3)

Allegro 5 API

## NAME

al\_fixatan2 - Allegro 5 API

## SYNOPSIS

-

  ```
  #include <allegro5/allegro.h>
  al_fixed al_fixatan2(al_fixed y, al_fixed x)
  ```

## DESCRIPTION

This is a fixed point version of the libc atan2() routine. It computes the arc tangent of `y / x`, but the signs of both arguments are used to determine the quadrant of the result, and `x` is permitted to be zero. This function is useful to convert Cartesian coordinates to polar coordinates.

Example:

-

  ```
  al_fixed result;
  /* Sets `result' to binary angle 64. */
  result = al_fixatan2(al_itofix(1), 0);
  /* Sets `result' 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());
  ```

## RETURN VALUE

Returns the arc tangent of `y / x` in fixed point binary format angle, from -128 to 128. If both `x` and `y` are zero, returns zero and sets Allegro’s errno to EDOM.