From Jason Turner

[any.nonmembers]

C++14 → C++17 3.0 KB 101 lines
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Archived: C++14 | C++17
Markdown: C++14 | C++17
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  1. tmp/tmpnsoz_b4r/{from.md → to.md} +98 -0
tmp/tmpnsoz_b4r/{from.md → to.md} RENAMED
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+ ### Non-member functions <a id="any.nonmembers">[[any.nonmembers]]</a>
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+
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+ ``` cpp
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+ void swap(any& x, any& y) noexcept;
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+ ```
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+
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+ *Effects:* As if by `x.swap(y)`.
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+
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+ ``` cpp
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+ template <class T, class... Args>
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+ any make_any(Args&& ...args);
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+ ```
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+
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+ *Effects:* Equivalent to:
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+ `return any(in_place_type<T>, std::forward<Args>(args)...);`
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+
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+ ``` cpp
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+ template <class T, class U, class... Args>
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+ any make_any(initializer_list<U> il, Args&& ...args);
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+ ```
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+
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+ *Effects:* Equivalent to:
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+ `return any(in_place_type<T>, il, std::forward<Args>(args)...);`
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+
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+ ``` cpp
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+ template<class T>
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+ T any_cast(const any& operand);
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+ template<class T>
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+ T any_cast(any& operand);
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+ template<class T>
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+ T any_cast(any&& operand);
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+ ```
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+
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+ Let `U` be the type `remove_cv_t<remove_reference_t<ValueType>>`.
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+
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+ *Requires:* For the first overload,
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+ `is_constructible_v<ValueType, const U&>` is `true`. For the second
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+ overload, `is_constructible_v<ValueType, U&>` is `true`. For the third
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+ overload, `is_constructible_v<ValueType, U>` is `true`. Otherwise the
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+ program is ill-formed.
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+
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+ *Returns:* For the first and second overload,
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+ `static_cast<ValueType>(*any_cast<U>(&operand))`. For the third
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+ overload, `static_cast<ValueType>(std::move(*any_cast<U>(&operand)))`.
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+
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+ *Throws:* `bad_any_cast` if
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+ `operand.type() != typeid(remove_reference_t<T>)`.
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+
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+ [*Example 1*:
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+
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+ ``` cpp
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+ any x(5); // x holds int
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+ assert(any_cast<int>(x) == 5); // cast to value
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+ any_cast<int&>(x) = 10; // cast to reference
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+ assert(any_cast<int>(x) == 10);
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+
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+ x = "Meow"; // x holds const char*
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+ assert(strcmp(any_cast<const char*>(x), "Meow") == 0);
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+ any_cast<const char*&>(x) = "Harry";
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+ assert(strcmp(any_cast<const char*>(x), "Harry") == 0);
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+
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+ x = string("Meow"); // x holds string
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+ string s, s2("Jane");
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+ s = move(any_cast<string&>(x)); // move from any
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+ assert(s == "Meow");
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+ any_cast<string&>(x) = move(s2); // move to any
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+ assert(any_cast<const string&>(x) == "Jane");
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+
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+ string cat("Meow");
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+ const any y(cat); // const y holds string
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+ assert(any_cast<const string&>(y) == cat);
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+
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+ any_cast<string&>(y); // error; cannot
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+ // any_cast away const
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+ ```
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+
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+ — *end example*]
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+
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+ ``` cpp
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+ template<class T>
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+ const T* any_cast(const any* operand) noexcept;
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+ template<class T>
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+ T* any_cast(any* operand) noexcept;
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+ ```
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+
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+ *Returns:* If `operand != nullptr && operand->type() == typeid(T)`, a
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+ pointer to the object contained by `operand`; otherwise, `nullptr`.
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+
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+ [*Example 2*:
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+
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+ ``` cpp
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+ bool is_string(const any& operand) {
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+ return any_cast<string>(&operand) != nullptr;
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+ }
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+ ```
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+
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+ — *end example*]
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+