c/numeric/complex/ctan

@1-3@ Computes the complex tangent of. @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 real version of the function tanh, implementing the formula $tan(iy) = i tanh(y)$, and the return type is imaginary.

Return value
If no errors occur, the complex tangent of is returned.

Errors and special cases are handled as if the operation is implemented by, where is the imaginary unit.