phase number => phase
Arguments and Values:
phase returns the phase of number (the angle part of its polar representation) in radians, in the range -<PI> (exclusive) if minus zero is not supported, or -<PI> (inclusive) if minus zero is supported, to <PI> (inclusive). The phase of a positive real number is zero; that of a negative real number is <PI>. The phase of zero is defined to be zero.
If number is a complex float, the result is a float of the same type as the components of number. If number is a float, the result is a float of the same type. If number is a rational or a complex rational, the result is a single float.
The branch cut for phase lies along the negative real axis, continuous with quadrant II. The range consists of that portion of the real axis between -<PI> (exclusive) and <PI> (inclusive).
The mathematical definition of phase is as follows:
(phase x) = (atan (imagpart x) (realpart x))
(phase 1) => 0.0s0 (phase 0) => 0.0s0 (phase (cis 30)) => -1.4159266 (phase #c(0 1)) => 1.5707964
Side Effects: None.
Affected By: None.
Should signal type-error if its argument is not a number. Might signal arithmetic-error.
Section 188.8.131.52 (Rule of Float Substitutability)