std::indirectly_readable(3)

🎀 NAME 🎀

std::indirectly_readable — okay bestie, this is literally the page for std::indirectly_readable(3), from the C++ Standard Libary manual (yes, that’s how the header spells it, and we’re moving on 💅). The name is the same as the thing, which is honestly iconic.

✨ Synopsis ✨

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>>;
    } &&
    (exposition only*)
    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>&
    >;

template< class In >
concept indirectly_readable =
    __IndirectlyReadableImpl<std::remove_cvref_t<In>>;

Plot twist: indirectly_readable is (since C++20) — she’s a modern girlie ✨

The concept indirectly_readable is modeled by types that are readable by applying operator*, such as pointers, smart pointers, and input iterators. It’s giving “dereference and read” energy, no cap.

🦋 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. That’s the whole vibe check, fr fr.

🌸 Equality preservation 🌸

Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise). Important little rule, bestie — don’t skip it.

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Source/version and date, cute sign-off: this page came from http://cppreference.com, dated 2024.06.10. Byeee, mwah 💅✨🫶