45             0 | 1 => y,   /* atan(+-0,+anything)=+-0 */  in atan2f()
46             2 => PI,      /* atan(+0,-anything) = pi */  in atan2f()
47             3 | _ => -PI, /* atan(-0,-anything) =-pi */  in atan2f()
58                 0 => PI / 4.,           /* atan(+INF,+INF) */  in atan2f()
59                 1 => -PI / 4.,          /* atan(-INF,+INF) */  in atan2f()
60                 2 => 3. * PI / 4.,      /* atan(+INF,-INF)*/  in atan2f()
61                 3 | _ => -3. * PI / 4., /* atan(-INF,-INF)*/  in atan2f()
65                 0 => 0.,      /* atan(+...,+INF) */  in atan2f()
66                 1 => -0.,     /* atan(-...,+INF) */  in atan2f()
67                 2 => PI,      /* atan(+...,-INF) */  in atan2f()
68                 3 | _ => -PI, /* atan(-...,-INF) */  in atan2f()
77     /* z = atan(|y/x|) with correct underflow */  in atan2f()
85         0 => z,                /* atan(+,+) */  in atan2f()
86         1 => -z,               /* atan(-,+) */  in atan2f()
87         2 => PI - (z - PI_LO), /* atan(+,-) */  in atan2f()
88         _ => (z - PI_LO) - PI, /* case 3 */ /* atan(-,-) */  in atan2f()