# Standard library header <experimental/ranges/utility>

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This header is part of the ranges library.

### Utility components

Defined in namespace `std::experimental::ranges`
swap | swaps the value of two objects (customization point object)
exchange | replaces the argument with a new value and returns its previous value (function template)

### Tag concepts

Defined in namespace `std::experimental::ranges`
TagSpecifier | specifies that a type is a tag specifier (concept)
TaggedType | specifies that a type represents a tag specifier and its element type (concept)

### Tagged pairs

Defined in namespace `std::experimental::ranges`
tagged | augument a tuple-like type with named accessors (class template)
tagged_pair | alias template for a tagged std::pair (alias template)
make_tagged_pair | convenience function for creating a `tagged_pair` (function template)

### Synopsis

    namespace std { namespace experimental { namespace ranges { inline namespace v1 {

    namespace {
      constexpr /* unspecified */ swap = /* unspecified */;
    }

    template<MoveConstructible T, class U = T>
      requires Assignable<T&, U>
    constexpr T exchange(T& obj, U&& new_val) noexcept(/* see definition */);

    template <class T>
    concept bool TagSpecifier = /* see definition */;

    template <class F>
    concept bool TaggedType = /* see definition */;

    template <class Base, TagSpecifier... Tags>
      requires sizeof...(Tags) <= std::tuple_size<Base>::value
    struct tagged;

    template <TaggedType T1, TaggedType T2>
    using tagged_pair = /* see definition */;

    template <TagSpecifier Tag1, TagSpecifier Tag2, class T1, class T2>
    constexpr /* see definition */ make_tagged_pair(T1&& x, T2&& y);

    }}}}

    namespace std {

    template <class Base, class... Tags>
    struct tuple_size<experimental::ranges::tagged<Base, Tags...>>;

    template <size_t N, class Base, class... Tags>
    struct tuple_element<N, experimental::ranges::tagged<Base, Tags...>>;

    }

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