-0 -> -0.000000, -0.0 -> -0.000000
atan2(+0, -0) = 3.141593
atan2(+0.0, -0.0) = 3.141593
atan2(-0, -0) = -3.141593
atan2(-0.0, -0.0) = -3.141593
atan2(+0, +0) = 0.000000
atan2(+0.0, +0.0) = 0.000000
atan2(-0, +0) = -0.000000
atan2(-0.0, +0.0) = -0.000000