check_electron_location_spatial Function

    function check_electron_location_spatial(orbs, ic, part_type) result(loc)
        ! same function as above, just for spatial orbitals
        integer, intent(in) :: orbs(2), ic, part_type
        integer :: loc
        character(*), parameter :: this_routine = "check_electron_location_spatial"

        integer :: i

        ASSERT(all(orbs >= [0, 0]))
        ASSERT(all(orbs <= [nBasis / 2, nBasis / 2]))

        if (ic == 1) then
            if (is_in_ref_spatial(orbs(1), part_type)) then
                ! this means the electron is in the reference determinant
                ! which means we should pick a hole also in the
                ! reference determinant, or otherwise we definetly
                ! increase the excitation level
                loc = 2
            else
                ! only option 0 and 2 for single excitations!
                loc = 0
            end if

        else if (ic == 2) then
            ! for double excitations we have to check both
            loc = 0
            do i = 1, 2
                if (is_in_ref_spatial(orbs(i), part_type)) then
                    loc = loc + 1
                end if
            end do
        end if

    end function check_electron_location_spatial