real(8) function zarg (z)
        implicit none
  c april 1977 version.  w. fullerton, c3, los alamos scientific lab.
        complex(8) 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