al_fixatan23
Allegro 5 api
Usage
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#include <allegro5/allegro.h> al_fixed al_fixatan2(al_fixed y, al_fixed x)
Overview
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:
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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.