V10/libj/atan2.c

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static qatan2();
atan2(xx, yy){
	register x, y;
	x=abs(xx);
	y=abs(yy);
	if(xx>=0 && yy>=0)
		return(qatan2(x, y));
	if(xx<0 && yy<=0)
		return(180+qatan2(x, y));
	if(xx<0 && yy>0)
		return(180-qatan2(x, y));
	return(360-qatan2(x, y));
}
static
qatan2(x, y)
	register x, y;
{
	if(x<y)
		return(90-(45*((long)x)/y));
	if(y==0)
		return(0);
	return(45*((long)y)/x);
}