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

        implicit none
  c april 1977 version.  w. fullerton, c3, los alamos scientific lab.

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

        external zatan
        data ci /(0.,1.)/
  c
        zatanh = -ci*zatan(ci*z)
  c
        return
        end