tmp/tmpy3flig4h/{from.md → to.md}
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| 1 |
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##### Class template `move_only_function` <a id="func.wrap.move.class">[[func.wrap.move.class]]</a>
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``` cpp
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namespace std {
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template<class... S> class move_only_function; // not defined
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template<class R, class... ArgTypes>
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class move_only_function<R(ArgTypes...) cv ref noexcept(noex)> {
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public:
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using result_type = R;
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// [func.wrap.move.ctor], constructors, assignment, and destructor
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move_only_function() noexcept;
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move_only_function(nullptr_t) noexcept;
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move_only_function(move_only_function&&) noexcept;
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template<class F> move_only_function(F&&);
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template<class T, class... Args>
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explicit move_only_function(in_place_type_t<T>, Args&&...);
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template<class T, class U, class... Args>
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explicit move_only_function(in_place_type_t<T>, initializer_list<U>, Args&&...);
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move_only_function& operator=(move_only_function&&);
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move_only_function& operator=(nullptr_t) noexcept;
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template<class F> move_only_function& operator=(F&&);
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~move_only_function();
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// [func.wrap.move.inv], invocation
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explicit operator bool() const noexcept;
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R operator()(ArgTypes...) cv ref noexcept(noex);
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// [func.wrap.move.util], utility
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void swap(move_only_function&) noexcept;
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friend void swap(move_only_function&, move_only_function&) noexcept;
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friend bool operator==(const move_only_function&, nullptr_t) noexcept;
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private:
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template<class VT>
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static constexpr bool is-callable-from = see below; // exposition only
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};
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}
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```
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The `move_only_function` class template provides polymorphic wrappers
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that generalize the notion of a callable object [[func.def]]. These
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wrappers can store, move, and call arbitrary callable objects, given a
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call signature.
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*Recommended practice:* Implementations should avoid the use of
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dynamically allocated memory for a small contained value.
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[*Note 1*: Such small-object optimization can only be applied to a type
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`T` for which `is_nothrow_move_constructible_v<T>` is
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`true`. — *end note*]
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