...
generic :: get => get_node_at_index, &
 get_node_at_index_user
procedure, private :: get_node_at_index, &
 get_node_at_index_user
...
abstract interface
 subroutine get_value(this_item, return_item)
 class(*), intent(in) :: this_item
 class(*), intent(out) :: return_item
 end subroutine get_value
end interface
...
subroutine get_node_at_index_user(this_list, node_index, func, return_item)
 class(child_list), intent(inout) :: this_list
 integer, intent(in) :: node_index
 procedure(get_value) :: func
 class(*), intent(out) :: return_item
 type(node), pointer :: curr_node
 integer index
 curr_node => this_list%head
 index = 1
 do while (associated(curr_node))
 if (index == node_index) then
 call func(curr_node%item, return_item)
 nullify (curr_node)
 return
 end if
 curr_node => curr_node%next
 index = index + 1
 end do
 nullify (curr_node)
end subroutine get_node_at_index_user
...

program main
 use linked_list_m, only: child_list, rk, ik
 implicit none
 real(rk) :: x
 integer(ik) :: n
 type(this_child) :: list
 print *, list%size()
 call list%push(1.0_rk)
 call list%push(2_ik)
 call list%get(1, get_value, x)
 call list%get(2, get_value, n)
 print *, x, n, list%size()
contains
 subroutine get_value(this_item, return_item)
 class(*), intent(in) :: this_item
 class(*), intent(out) :: return_item
 select type (this_item)
 type is (real(rk))
 select type (return_item)
 type is (real(rk))
 return_item = this_item
 class default
 print *, '*<ERROR>* get_value: type mismatch'
 end select
 type is (integer(ik))
 select type (return_item)
 type is (integer(ik))
 return_item = this_item
 class default
 print *, '*<ERROR>* get_value: type mismatch'
 end select
 class default
 print *, "*<ERROR>* get_value: invalid type"
 end select
 end subroutine get_value
end program main