[b276be5] | 1 | #pragma once |
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| 2 | |
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| 3 | #include <exception> |
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| 4 | #include <memory> |
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| 5 | #include <string> |
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| 6 | #include <typeinfo> |
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| 7 | #include <typeindex> |
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| 8 | |
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| 9 | class bad_cast : public std::exception { |
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| 10 | std::string why; |
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| 11 | public: |
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| 12 | bad_cast( const std::type_index& f, const std::type_index& t ) : std::exception() { |
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| 13 | why = std::string{"bad cast of "} + f.name() + " to " + t.name(); |
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| 14 | } |
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| 15 | |
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| 16 | ~bad_cast() override = default; |
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| 17 | |
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| 18 | const char* what() const noexcept override { return why.c_str(); } |
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| 19 | }; |
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| 20 | |
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| 21 | class object { |
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| 22 | public: |
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| 23 | std::type_index get_class() const { return { typeid(*this) }; } |
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| 24 | |
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| 25 | template<typename T> |
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| 26 | T& as() { |
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| 27 | std::type_index from = get_class(), to = { typeid(T) }; |
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| 28 | if ( from != to ) throw bad_cast{ from, to }; |
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| 29 | return reinterpret_cast<T&>(*this); |
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| 30 | } |
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| 31 | |
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| 32 | template<typename T> |
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| 33 | const T& as() const { |
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| 34 | std::type_index from = get_class(), to = { typeid(T) }; |
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| 35 | if ( from != to ) throw bad_cast{ from, to }; |
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| 36 | return reinterpret_cast<const T&>(*this); |
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| 37 | } |
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| 38 | |
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| 39 | virtual std::unique_ptr<object> new_inst() const = 0; |
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| 40 | |
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| 41 | virtual std::unique_ptr<object> new_copy() const = 0; |
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| 42 | |
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| 43 | virtual object& operator= (const object&) = 0; |
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| 44 | |
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| 45 | virtual ~object() = default; |
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| 46 | }; |
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| 47 | |
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| 48 | class integer : public object { |
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| 49 | private: |
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| 50 | int x; |
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| 51 | |
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| 52 | public: |
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| 53 | integer() = default; |
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| 54 | |
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| 55 | integer(int x) : x(x) {} |
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| 56 | |
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| 57 | std::unique_ptr<object> new_inst() const override { return std::make_unique<integer>(); } |
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| 58 | |
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| 59 | std::unique_ptr<object> new_copy() const override { return std::make_unique<integer>(*this); } |
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| 60 | |
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| 61 | integer& operator= (const integer& that) { |
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| 62 | x = that.x; |
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| 63 | return *this; |
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| 64 | } |
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| 65 | |
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| 66 | object& operator= (const object& that) override { |
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| 67 | std::type_index from = that.get_class(), to = get_class(); |
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| 68 | if ( from != to ) throw bad_cast{ from, to }; |
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| 69 | return *this = reinterpret_cast<const integer&>(that); |
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| 70 | } |
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| 71 | |
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| 72 | ~integer() override = default; |
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| 73 | |
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| 74 | integer& operator+= (const integer& that) { |
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| 75 | x += that.x; |
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| 76 | return *this; |
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| 77 | } |
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| 78 | }; |
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