build_nfa_graph Subroutine

   pure subroutine build_nfa_graph (tree, nfa, nfa_entry, nfa_exit, nfa_top, all_segments)
      use :: forgex_parameters_m, only: NFA_TRANSITION_UNIT
      implicit none
      type(tree_t),         intent(in)                :: tree
      type(nfa_state_node_t), intent(inout), allocatable :: nfa(:)
      integer(int32),         intent(inout)              :: nfa_entry
      integer(int32),         intent(inout)              :: nfa_exit
      integer(int32),         intent(inout)              :: nfa_top
      type(segment_t),        intent(inout), allocatable :: all_segments(:)


      integer(int32) :: i, i_begin, i_end ! index for states array

      i_begin = NFA_STATE_BASE
      i_end   = NFA_STATE_UNIT

      ! initialize
      nfa_top = 0

      allocate(nfa(i_begin:i_end))

      ! Initialize
      nfa(i_begin:i_end)%own_i = [(i, i =i_begin, i_end)]

      nfa(:)%alloc_count_f = 0
      nfa(:)%alloc_count_b = 0

      nfa(:)%forward_top = 1
      nfa(:)%backward_top = 1


      call make_nfa_node(nfa_top)
      nfa_entry = nfa_top

      call make_nfa_node(nfa_top)
      nfa_exit = nfa_top

      call generate_nfa(tree, tree%top, nfa, nfa_top, nfa_entry, nfa_exit)

      do i = 1, nfa_top
         call nfa(i)%merge_segments()
      end do

      call disjoin_nfa(nfa, nfa_top, all_segments)

   end subroutine build_nfa_graph