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

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

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

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

  c
        zcosh = cos (ci*z)
  c
        return
        end