#include "mathx.h"
#include <math.h>

//	Array of angles in degrees associated with arctan values

const char arctan_array[] =
{
    0,	 1,	 1,	 2,	 2,	 3,	 3,	 4,	 5,	 5,
	6,	 6,	 7,	 7,	 8,	 9,	 9,	10,	10,	11,
	11, 12,	12,	13,	13,	14,	15,	15,	16,	16,
	17,	17,	18,	18,	19,	19,	20,	20,	21,	21,
	22,	22,	23,	23,	24,	24,	25,	25,	26,	26,
	27,	27,	27,	28,	28,	29,	29,	30,	30,	31,
	31,	31,	32,	32,	33,	33,	33,	34,	34,	35,
	35,	35,	36,	36,	37,	37,	37,	38,	38,	38,
	39,	39,	39,	40,	40,	40,	41,	41,	41,	42,
	42,	42,	43,	43,	43,	44,	44,	44,	44,	45
};

// 	Rough integer approximation (fast) of arctan2 based on table for 0-45 degrees
//	Return degrees, base on integer y and x inputs to arctan

int Arctan2(int y, int x)
{
	int xneg=0,yneg=0;
    int index,angle=45;

    if (x < 0)
	{ 
        xneg = 1;
        x = -x;
   	}

    if (y < 0)
	{
        yneg = 1;
        y = -y;
   	}

    if (x == 0 && y == 0) return 0;

    if (y == 0)
        return(xneg ? 180 : 0);

    if (x == 0)
        return(yneg ? 270 : 90);

    if (x > y)
	{
        index = (int)(((long)y * INTEGER_ARCTAN) / (long)x);
        angle = arctan_array[index];
   	}
	else if (y > x)
	{
        index = (int)(((long)x * INTEGER_ARCTAN) / (long)y);
        angle = 90 - arctan_array[index];
   	}
    
    if (xneg)
        if (yneg) 
            return(180 + angle);
        else
            return(180 - angle);
    else
        if (yneg) 
            return(360 - angle);
        else
            return(angle);
        
}