generate_nfa_closure Subroutine

   pure recursive subroutine generate_nfa_closure(tree, idx, nfa_graph, nfa_top, entry, exit)
      implicit none
      type(tree_t),  intent(in) :: tree
      type(nfa_state_node_t), allocatable, intent(inout) :: nfa_graph(:)
      integer(int32), intent(in) :: idx
      integer(int32), intent(inout) :: nfa_top
      integer(int32), intent(in) :: entry
      integer(int32), intent(in) :: exit

      integer(int32) :: node1, node2

      call make_nfa_node(nfa_top)
      if (is_exceeded(nfa_top, nfa_graph)) then
         call reallocate_nfa(nfa_graph)
      end if
      node1 = nfa_top

      call make_nfa_node(nfa_top)
      if (is_exceeded(nfa_top, nfa_graph)) then
         call reallocate_nfa(nfa_graph)
      end if
      node2 = nfa_top

      call nfa_graph(entry)%add_transition(nfa_graph, entry, node1, SEG_EPSILON)

      call generate_nfa(tree, tree%nodes(idx)%left_i, nfa_graph, nfa_top, node1, node2)

      call nfa_graph(node2)%add_transition(nfa_graph, node2, node1, SEG_EPSILON)
      call nfa_graph(node1)%add_transition(nfa_graph, node1, exit, SEG_EPSILON)

   end subroutine generate_nfa_closure