73 atan(double x)  in atan()  argument
78 	GET_HIGH_WORD(hx,x);  in atan()
82 	    GET_LOW_WORD(low,x);  in atan()
85 		return x+x;		/* NaN */  in atan()
90 		if(huge+x>one) return x;	/* raise inexact */  in atan()
94 	x = fabs(x);  in atan()
97 		id = 0; x = (2.0*x-one)/(2.0+x);  in atan()
99 		id = 1; x  = (x-one)/(x+one);  in atan()
103 		id = 2; x  = (x-1.5)/(one+1.5*x);  in atan()
105 		id = 3; x  = -1.0/x;  in atan()
109 	z = x*x;  in atan()
114 	if (id<0) return x - x*(s1+s2);  in atan()
116 	    z = atanhi[id] - ((x*(s1+s2) - atanlo[id]) - x);  in atan()