VMS Help RTL Routines, MTH$, MTH$CLOG, Argument  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 complex-number

    OpenVMS usage:complex_number
    type:         F_floating complex
    access:       read only
    mechanism:    by reference

    Complex number whose complex natural logarithm is to be returned.
    This complex number has the form (r,i), where r is the real part
    and i is the imaginary part. The complex-number argument is the
    address of this complex number. For MTH$CLOG, complex-number
    specifies an F-floating number.