generate_nfa_concatenate Subroutine

   pure recursive subroutine generate_nfa_concatenate(tree, idx, nfa, entry_i, exit_i)
      implicit none
      type(tree_t), intent(in) :: tree
      type(nfa_graph_t), intent(inout) :: nfa
      integer(int32), intent(in) :: idx
      integer(int32), intent(in) :: entry_i, exit_i

      integer(int32) :: node1

      call nfa%new_nfa_node()
      if (nfa%is_exceeded()) call nfa%reallocate()

      node1 = nfa%top

      call generate_nfa(tree, tree%nodes(idx)%left_i, nfa, entry_i, node1)
      call generate_nfa(tree, tree%nodes(idx)%right_i, nfa, node1, exit_i)

   end subroutine generate_nfa_concatenate