real(kind(1.d0)) function zarg (z)
      implicit none
c april 1977 version.  w. fullerton, c3, los alamos scientific lab.
      complex(kind(1.d0)) z

c
      zarg = 0.0
      if (real(z).ne.0. .or. aimag(z).ne.0.) zarg =
     1  atan2 (aimag(z), real(z))
c
      return
      end