dfa.h

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#pragma once
 
#include <cstdint>
 
#include <absl/container/btree_map.h>
 
#include "automaton/automaton.h"
 
namespace automaton {
 
class DFANode {
public:
    struct Lt {
        constexpr bool operator()(const DFANode* n, const DFANode* m) const noexcept { return n->id() < m->id(); }
    };
 
    DFANode(int id)
        : id_(id) {}
 
    constexpr int id() const noexcept { return id_; }
    void add_transition(const DFANode* to, std::uint16_t c);
    const DFANode* get_transition(std::uint16_t c) const;
 
    // F: void(const DFANode*)
    template<class F> void for_transitions(F&& f, std::uint16_t c) const {
        if (erroring_) return;
        if (auto it = transitions_.find(c); it != transitions_.end()) f(it->second);
    }
 
    // F: void(std::uint16_t, const DFANode*)
    template<class F> void for_transitions(F&& f) const {
        if (erroring_) return;
        for (auto& [c, to] : transitions_) f(c, to);
    }
 
    bool is_accepting() const noexcept { return accepting_; }
    void set_accepting(bool accepting) noexcept {
        assert(!(accepting && erroring_) && "state cannot be accepting and erroring");
        accepting_ = accepting;
    }
 
    bool is_erroring() const noexcept { return erroring_; }
    void set_erroring(bool erroring) noexcept {
        assert(!(accepting_ && erroring) && "state cannot be accepting and erroring");
        erroring_ = erroring;
    }
 
    friend std::ostream& operator<<(std::ostream& os, const DFANode& node);
 
private:
    int id_;
    absl::flat_hash_map<std::uint16_t, const DFANode*> transitions_;
    bool accepting_ = false;
    bool erroring_  = false;
};
 
extern template class AutomatonBase<DFANode>;
 
class DFA : public AutomatonBase<DFANode> {
public:
    DFA()                      = default;
    DFA(const DFA&)            = delete;
    DFA& operator=(const DFA&) = delete;
 
    enum SpecialTransitons : std::uint16_t {};
};
 
template<class To> using DFAMap = absl::btree_map<const DFANode*, To, DFANode::Lt>;
 
} // namespace automaton