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    cpp/iterator/indirectly readable: Difference between revisions

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    {{dcl|notes={{mark expos}}|1=
    {{dcl|notes={{mark expos}}|1=
    template< class In >
    template< class In >
      concept __IndirectlyReadableImpl =
    concept __IndirectlyReadableImpl =
        requires(const In in) {
    requires(const In in) {
          typename std::iter_value_t<In>;
    typename std::iter_value_t<In>;
          typename std::iter_reference_t<In>;
    typename std::iter_reference_t<In>;
          typename std::iter_rvalue_reference_t<In>;
    typename std::iter_rvalue_reference_t<In>;
          { *in } -> std::same_as<std::iter_reference_t<In>>;
    { *in } -> std::same_as<std::iter_reference_t<In>>;
          { ranges::iter_move(in) } -> std::same_as<std::iter_rvalue_reference_t<In>>;
    { ranges::iter_move(in) } -> std::same_as<std::iter_rvalue_reference_t<In>>;
        } &&
    } &&
        std::common_reference_with<
    std::common_reference_with<
          std::iter_reference_t<In>&&, std::iter_value_t<In>&
    std::iter_reference_t<In>&&, std::iter_value_t<In>&
        > &&
    > &&
        std::common_reference_with<
    std::common_reference_with<
          std::iter_reference_t<In>&&, std::iter_rvalue_reference_t<In>&&
    std::iter_reference_t<In>&&, std::iter_rvalue_reference_t<In>&&
        > &&
    > &&
        std::common_reference_with<
    std::common_reference_with<
          std::iter_rvalue_reference_t<In>&&, const std::iter_value_t<In>&
    std::iter_rvalue_reference_t<In>&&, const std::iter_value_t<In>&
        >;
    >;
    }}
    }}
    {{dcl|since=c++20|1=
    {{dcl|since=c++20|1=
    template< class In >
    template< class In >
      concept indirectly_readable =
    concept indirectly_readable =
        __IndirectlyReadableImpl<std::remove_cvref_t<In>>;
    __IndirectlyReadableImpl<std::remove_cvref_t<In>>;
    }}
    }}
    {{dcl end}}
    {{dcl end}}

    Latest revision as of 06:23, 1 October 2023

     
    C++
     
    Iterator library
    Iterator concepts
    Iterator primitives
    Algorithm concepts and utilities
    Indirect callable concepts
    Common algorithm requirements
    (C++20)
    (C++20)
    (C++20)
    Utilities
    (C++20)
    Iterator adaptors
    Range access
    (C++11)(C++14)
    (C++14)(C++14)  
    (C++11)(C++14)
    (C++14)(C++14)  
    (C++17)(C++20)
    (C++17)
    (C++17)
     
    Defined in header <iterator> 
    template< class In >
    concept __IndirectlyReadableImpl =
        requires(const In in) {
            typename std::iter_value_t<In>;
            typename std::iter_reference_t<In>;
            typename std::iter_rvalue_reference_t<In>;
            { *in } -> std::same_as<std::iter_reference_t<In>>;
            { ranges::iter_move(in) } -> std::same_as<std::iter_rvalue_reference_t<In>>;
        } &&
        std::common_reference_with<
            std::iter_reference_t<In>&&, std::iter_value_t<In>&
        > &&
        std::common_reference_with<
            std::iter_reference_t<In>&&, std::iter_rvalue_reference_t<In>&&
        > &&
        std::common_reference_with<
            std::iter_rvalue_reference_t<In>&&, const std::iter_value_t<In>&
        >;
    		(exposition only*) 
    template< class In >
    concept indirectly_readable =
        __IndirectlyReadableImpl<std::remove_cvref_t<In>>;
    		(since C++20)

    The concept indirectly_readable is modeled by types that are readable by applying operator*, such as pointers, smart pointers, and input iterators.

    Semantic requirements

    Given a value i of type I, I models indirectly_readable only if all concepts it subsumes are modeled and the expression *i is equality-preserving.

    Equality preservation

    Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise).