complex(kind(1.d0)) function ztanh (z)

  c april 1977 version.  w. fullerton, c3, los alamos scientific lab.

        complex(kind(1.d0)) z, ci, ztan

        external ztan

        data ci /(0.d0,1.d0)/

  c
        ztanh = -ci*ztan(ci*z)
  c
        return
        end