external_lMat_matel Function

    function external_lMat_matel(nI, ex) result(matel)
        ! @note
        ! this function should normally be pure but the tchint function is not,
        ! so until that has been modified to be pure, this function will be impure
        ! @endnote
        integer, intent(in) :: nI(:)
        integer, intent(in) :: ex(:,:)
        HElement_t(dp) :: matel

#ifdef USE_TCHINT_
        matel = tc_matel_L_contrib_simple(nI, ex)
#else
        character(*), parameter :: t_r = "external_lMat_matel"
        unused_var(nI); unused_var(ex); unused_var(matel)
        call stop_all(t_r, "Did not compile with TCHINT support")
#endif

    end function external_lMat_matel