transition-map.hh

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#ifndef VCSN_CORE_TRANSITION_MAP_HH
# define VCSN_CORE_TRANSITION_MAP_HH

# include <map>
# include <type_traits>

namespace vcsn
{
  namespace detail
  {

    template <typename Aut,
              typename WeightSet = weightset_t_of<Aut>,
              bool Deterministic = false,
              bool AllOut = false,
              bool KeepTransitions = false>
    class transition_map
    {
    public:
      using state_t = state_t_of<Aut>;
      using transition_t = transition_t_of<Aut>;
      using weightset_t = WeightSet;
      using weight_t = typename weightset_t::value_t;

      template <bool KeepTransitions_ = false, typename Dummy = void>
      struct transition_
      {
        transition_(weight_t w, state_t d, transition_t)
          : wgt(w)
          , dst(d)
        {}
        weight_t wgt;
        state_t dst;
      };

      template <typename Dummy>
      struct transition_<true, Dummy>
      {
        weight_t wgt;
        state_t dst;
        transition_t_of<Aut> transition;
      };

      using transition = transition_<KeepTransitions>;

      using transitions_t
        = typename std::conditional<Deterministic,
                                    transition,
                                    std::vector<transition>>::type;
      using map_t = std::map<label_t_of<Aut>, transitions_t>;

      transition_map(const Aut& aut, const weightset_t& ws)
        : aut_(aut)
        , ws_(ws)
      {}

      transition_map(const Aut& aut)
        : transition_map(aut, *aut->weightset())
      {}

      map_t& operator[](state_t s)
      {
        auto lb = maps_.lower_bound(s);
        if (lb == maps_.end() || maps_.key_comp()(s, lb->first))
          return build_map_(lb, s);
        else
          return lb->second;
      }

    private:
      using maps_t = std::map<state_t, map_t>;

      template <bool Deterministic_>
      void
      insert_(map_t& map,
              label_t_of<Aut> l, transition t,
              typename std::enable_if<Deterministic_>::type* = nullptr)
      {
        map.emplace(l, t);
      }

      template <bool Deterministic_>
      void
      insert_(map_t& map,
              label_t_of<Aut> l, transition t,
              typename std::enable_if<!Deterministic_>::type* = nullptr)
      {
        map[l].emplace_back(t);
      }

      map_t&
      build_map_(typename maps_t::iterator lb, state_t s)
      {
        auto& res = maps_.emplace_hint(lb, s, map_t{})->second;
        for (auto t: aut_->all_out(s))
          if (AllOut || !aut_->labelset()->is_special(aut_->label_of(t)))
            {
              auto w = ws_.conv(*aut_->weightset(), aut_->weight_of(t));
              insert_<Deterministic>(res,
                                     aut_->label_of(t),
                                     transition{w, aut_->dst_of(t), t});
            }
        return res;
      }

      maps_t maps_;
      const Aut& aut_;
      const weightset_t& ws_;
    };
  }
}

#endif // !VCSN_CORE_TRANSITION_MAP_HH