std::projected_value_t(3)

📦 version 2024.07.05, in nixpkgs unstable, opensuse-leap 16.0

💖 std::projected_value_t(3) 💖

okay bestie, welcome to the std::projected_value_t(3) page from the C++ Standard Libary — manual name folded in near the top, just like we said, and we are not copying the whole header line because we have main character energy today ✨

🌸 NAME 🌸

std::projected_value_t — and the one-liner is literally also std::projected_value_t. iconic self-reference, no notes 💅

📜 Synopsis 📜

Defined in header <iterator>:

template< std::indirectly_readable I,
          std::indirectly_regular_unary_invocable<I> Proj >
using projected_value_t =
    std::remove_cvref_t<std::invoke_result<Proj&,
        std::iter_value_t<I>&>>;

(since C++26)

so here's the tea 🫖: the alias template projected_value_t obtains the value type by stripping any reference and its topmost cv-qualifiers from the result type of applying Proj to std::iter_value_t<I>&.

and yes, projected_value_t is used to determine the default value type in some algorithms such as ranges::contains. slay 💖

🧚 Template parameters 🧚

  • I — an indirectly readable type
  • Proj — projection applied to an lvalue reference to value type of I

✨ Notes ✨

feature-test macro check, bestie 👑

  • Feature-test macro: __cpp_lib_default_template_type_for_algorithm_values
  • Value: 202403L
  • Std: (C++26)
  • Feature: default template type for algorithm values using std::projected_value_t

🎀 Example 🎀

This section is incomplete Reason: no example 😭

🦋 See also 🦋

  • indirect_result_t (C++20) — computes the result of invoking a callable object on the result of dereferencing some set of indirectly_readable types (alias template)
  • projected (C++20) — helper template for specifying the constraints on algorithms that accept projections (class template)

🏷️ Category 🏷️

  • Todo no example 🙈

mwah 💋 — source and version/date sign-off: http://cppreference.com, 2024.06.10, page std::projected_value_t(3). periodt 🌈

📦 where this page comes from