1submodule (parent:container) helper
2  implicit none
3
4contains
5
6  module function parent_distance(pa, pb) result(dist)
7    type(parent_type), intent(in) :: pa, pb
8    real :: dist
9
10    dist = sqrt(parent_weight(pa) + parent_weight(pb))
11  end function parent_distance
12
13end submodule helper
14