59 lines
1.1 KiB
C++
59 lines
1.1 KiB
C++
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template <class T>
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class maybe
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{
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private:
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bool present;
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T v;
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public:
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maybe () : present(0) { }
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maybe (const T &v_) : present(1), v(v_) { }
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maybe (const maybe &m) : present(m.present), v(m.v) { }
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maybe (reader &r);
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~maybe () { }
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maybe &operator = (const maybe &m) { present = m.present; v = m.v; return *this; }
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bool is_some () const { return present; }
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bool is_none () const { return !present; }
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T &some () { assert (present); return v; }
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bool operator == (const maybe &m) const
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{
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if (present != m.present)
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return 0;
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if (present)
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return v == m.v;
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}
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bool operator != (const maybe &m) const { return !operator == (m); }
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void write_self (writer &w) const;
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hash_t hash_self () const;
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};
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template<class T>
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maybe<T>::maybe (reader &r)
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{
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read (r, present);
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if (present)
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read (r, v);
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}
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template<class T> void
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maybe<T>::write_self (writer &w) const
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{
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write (w, present);
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if (present)
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write (w, v);
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}
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template<class T> hash_t
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maybe<T>::hash_self () const
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{
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if (present)
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return hash_combine (hash (0xdeadbeef), hash (v));
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else
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return hash (0xcafebabe);
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}
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