c/numeric/complex/cacosh

@1-3@ Computes complex arc hyperbolic cosine of a complex value with branch cut at values less than 1 along the real axis. @4@ Type-generic macro: If has type,  is called. if has type,  is called, if  has type ,  is called. If is real or integer, then the macro invokes the corresponding real function. If is imaginary, then the macro invokes the corresponding complex number version and the return type is complex.

Return value
The complex arc hyperbolic cosine of in the interval $[0; ∞)$ along the real axis and in the interval $[−iπ; +iπ]$ along the imaginary axis.

Error handling and special values
Errors are reported consistent with math_errhandling

If the implementation supports IEEE floating-point arithmetic,
 * If is, the result is
 * If is  (for any finite x), the result is
 * If is  (for non-zero finite x), the result is  and fe_invalid may be raised.
 * If is, the result is , where the sign of the imaginary part is unspecified
 * If is  (for any positive finite y), the result is
 * If is  (for any positive finite y), the result is
 * If is, the result is
 * If is, the result is
 * If is, the result is
 * If is  (for any finite y), the result is  and fe_invalid may be raised.
 * If is, the result is
 * If is, the result is
 * If is, the result is