dot_prod_not_implemented Function

    function dot_prod_not_implemented(this, k_vec, r_vec) result(dot)
        ! for the "fourier transform" implement the correct
        ! dot-product with all the factors of pi and n_sites implemented
        ! for each lattice
        class(lattice) :: this
        integer, intent(in) :: k_vec(3), r_vec(3)
        real(dp) :: dot
        character(*), parameter :: this_routine = "dot_prod_not_implemented"

        unused_var(this)
        unused_var(k_vec)
        unused_var(r_vec)

        call stop_all(this_routine, "not yet implemented for this lattice type!")
#ifdef WARNING_WORKAROUND_
        dot = 0.0_dp
        unused_var(this)
        unused_var(k_vec)
        unused_var(r_vec)
#endif

        dot = 0.0_dp

    end function dot_prod_not_implemented