function carg (z)
  c april 1977 version.  w. fullerton, c3, los alamos scientific lab.
        complex z
  c      external atan2
  c
        carg = 0.0
        if (real(z).ne.0. .or. aimag(z).ne.0.) carg =
       1  atan2 (aimag(z), real(z))
  c
        return
        end