extract_1_rdm_ind Subroutine

    pure subroutine extract_1_rdm_ind(rdm_ind, i, a, excit_lvl, excit_typ)
        ! the converstion routine between the combined and explicit rdm
        ! indices for the 1-RDM
        integer(int_rdm), intent(in) :: rdm_ind
        integer, intent(out) :: i, a
        integer, intent(out), optional :: excit_lvl, excit_typ

        integer(int_rdm) :: rdm_ind_

        ! if we also want to use the top 7 bits of rdm_ind for information
        ! of the excit-lvl and type we have to 0 them out before
        ! extracting the indices

        rdm_ind_ = iand(rdm_ind, rdm_ind_bitmask)

        a = int(mod(rdm_ind_ - 1, nSpatOrbs) + 1)
        i = int((rdm_ind_ - 1) / nSpatOrbs + 1)

        if (present(excit_lvl)) then
            excit_lvl = extract_excit_lvl_rdm(rdm_ind)
        end if

        if (present(excit_typ)) then
            excit_typ = extract_excit_type_rdm(rdm_ind)
        end if

    end subroutine extract_1_rdm_ind