clog() returns the natural logarithm of a complex number.

    clog(x,y) is defined as ln(x + iy) = 1/2 ln(x**2 + y**2) + i *
    atan2(y,x).

                           Entry-Point Names

    Generic
    Function   Data Type   OpenVMS        Tru64 UNIX
    Name       Required

    clog       S_FLOAT     math$clog_s    clogf
               T_FLOAT     math$clog_t    clog
               X_FLOAT     math$clog_x    clogl
               F_FLOAT     math$clog_f
               G_FLOAT     math$clog_g