std::indire...ble_storable(3)

💖 NAME 💖

std::indirectly_copyable_storable - std::indirectly_copyable_storable

okay so welcome to the std::indire...ble_storable(3) page from the C++ Standard Libary manual, bestie 💅 the NAME line is literally doing the “same thing twice” thing and honestly? iconic. This is all about the std::indirectly_copyable_storable concept, and we’re gonna unpack it fr fr.

✨ Synopsis ✨

It’s defined in the header <iterator>, no cap. Here’s the exact synopsis, untouched and slaying in its natural habitat:

          Defined in header <iterator>
          template< class In, class Out >

          concept indirectly_copyable_storable =
              std::indirectly_copyable<In, Out> &&
              std::indirectly_writable<Out, std::iter_value_t<In>&> &&
              std::indirectly_writable<Out, const std::iter_value_t<In>&> &&
              std::indirectly_writable<Out, std::iter_value_t<In>&&> &&
       (since C++20)
              std::indirectly_writable<Out, const std::iter_value_t<In>&&> &&
              std::copyable<std::iter_value_t<In>> &&
              std::constructible_from<std::iter_value_t<In>,
          std::iter_reference_t<In>> &&

              std::assignable_from<std::iter_value_t<In>&,
          std::iter_reference_t<In>>;

The indirectly_copyable_storable concept specifies the relationship between an indirectly_readable type and an indirectly_writable type. In addition to indirectly_copyable, this concept specifies that the copy from the indirectly_readable type can be performed via an intermediate object. that’s the tea ☕✨

🧠 Semantic requirements 🧠

In and Out model std::indirectly_copyable_storable<In, Out> only if given a dereferenceable value i of type In:

• After the definition std::iter_value_t<In> obj(*i);, obj is equal to the value previously denoted by *i, and
• if std::iter_reference_t<In> is an rvalue reference type, *i is placed in a valid but unspecified state after the initialization of obj.

like, the vibe check here is real: the value has to actually match, and if it’s an rvalue reference situation, *i ends up valid but unspecified after obj gets initialized 🫶

🌈 Equality preservation 🌈

Expressions declared in requires expressions of the standard library concepts are required to be equality-preserving (except where stated otherwise). periodt — that’s the rule, bestie 💖

👀 See also 👀

• indirectly_copyable (C++20) — specifies that values may be copied from an indirectly_readable type to an indirectly_writable type (concept)
• indirectly_movable_storable (C++20) — specifies that values may be moved from an indirectly_readable type to an indirectly_writable type and that the move may be performed via an intermediate object (concept)

💖 cute little source/version/date sign-off: this page came from http://cppreference.com, version date 2024.06.10, and it’s the std::indire...ble_storable(3) page — bye bestie, go model some concepts 💅✨🎀