std::type_identity(3)

💖 std::type_identity(3) — C++ Standard Libary 💖

okay so bestie, this is the manual page for std::type_identity(3) from the C++ Standard Libary. Let's get into it.

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✨ NAME ✨

std::type_identity - std::type_identity

🦋 Synopsis 🦋

Defined in header <type_traits>:

template< class T >              (since C++20)
struct type_identity;

It provides the member typedef type that names T (i.e., the identity transformation).

bestie, if the program adds specializations for std::type_identity, the behavior is undefined. Like, do not do that. 💀

🌸 Member types 🌸

• Name: type — Definition: T

🎀 Helper types 🎀

template< class T >                              (since C++20)
using type_identity_t = type_identity<T>::type;

🧚 Possible implementation 🧚

template<class T>
struct type_identity { using type = T; };

👑 Notes 👑

std::type_identity can be used to establish non-deduced contexts in template argument deduction. slay.

Feature-test macro vibes:

• Feature-test macro: __cpp_lib_type_identity
• Value: 201806L
• Std: (C++20)
• Feature: std::type_identity

🔥 Example 🔥

Run this code (// Run this code):

#include <iostream>
#include <type_traits>

template<class T>
T foo(T a, T b) { return a + b; }

template<class T>
T bar(T a, std::type_identity_t<T> b) { return a + b; }

int main()
{
    // foo(4.2, 1); // error, deduced conflicting types for 'T'
    std::cout << bar(4.2, 1) << '\n';  // OK, calls bar<double>
}

🍓 Output 🍓

5.2

🌈 See also 🌈

• identity — function object that returns its argument unchanged — (C++20) — (class)

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that's the whole vibe, bestie 🫶 — source/version: http://cppreference.com, date: 2024.06.10. periodt 💅