std::make_tuple(3)

💖 std::make_tuple 💖

okay so welcome to the std::make_tuple(3) page from the C++ Standard Libary manual — yes, that’s the manual name, we’re keeping it exactly, no cap. This is the one where C++ looks at your pile of arguments and goes “I gotchu, let’s make a tuple,” and deduces the target type from their types. slay. ✨

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🌸 NAME 🌸

std::make_tuple — std::make_tuple

yeah bestie, the NAME section is literally that. iconic minimalism. 💅

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✨ Synopsis ✨

Defined in header <tuple>
template< class... Types >                            (since C++11)
std::tuple<VTypes...> make_tuple( Types&&... args );  (constexpr
since C++14)

Creates a tuple object, deducing the target type from the types of arguments.

For each Ti in Types..., the corresponding type Vi in VTypes... is std::decay<Ti>::type — unless application of std::decay results in std::reference_wrapper<X> for some type X, in which case the deduced type is X&. the way this deduction logic is doing the absolute most and still serving exactly what it needs to serve. 🦋

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🎀 Parameters 🎀

• args — zero or more arguments to construct the tuple from.

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🫶 Return value 🫶

A std::tuple object containing the given values, created as if by std::tuple<VTypes...>(std::forward<Types>(t)...). periodt. ✨

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🧚 Possible implementation 🧚

here’s a possible implementation, and yes it’s giving template wizardry:

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

template <class T>
struct unwrap_refwrapper<std::reference_wrapper<T>>
{
    using type = T&;
};

template <class T>
using unwrap_decay_t = typename unwrap_refwrapper<typename
std::decay<T>::type>::type;
// or use std::unwrap_ref_decay_t (since C++20)

template <class... Types>
constexpr // since C++14
std::tuple<unwrap_decay_t<Types>...> make_tuple(Types&&... args)
{
    return
std::tuple<unwrap_decay_t<Types>...>(std::forward<Types>(args)...);
}

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🌈 Example 🌈

// Run this code — here’s the whole example, fr fr:

#include <iostream>
#include <tuple>
#include <functional>

std::tuple<int, int> f() // this function returns multiple values
{
    int x = 5;
    return std::make_tuple(x, 7); // return {x,7}; in C++17
}

int main()
{
    // heterogeneous tuple construction
    int n = 1;
    auto t = std::make_tuple(10, "Test", 3.14, std::ref(n), n);
    n = 7;
    std::cout << "The value of t is ("
              << std::get<0>(t) << ", "
              << std::get<1>(t) << ", "
              << std::get<2>(t) << ", "
              << std::get<3>(t) << ", "
              << std::get<4>(t) << ")\n";

    // function returning multiple values
    int a, b;
    std::tie(a, b) = f();
    std::cout << a << ' ' << b << '\n';
}

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💫 Output 💫

The value of t is (10, Test, 3.14, 7, 1)
5 7

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👑 See also 👑

more tuple lore, iykyk: 💜

• tie — creates a tuple of lvalue references or unpacks a tuple into individual objects. (C++11) (function template)
• forward_as_tuple — creates a tuple of forwarding references. (C++11) (function template)
• tuple_cat — creates a tuple by concatenating any number of tuples. (C++11) (function template)
• apply — calls a function with a tuple of arguments. (C++17) (function template)

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mwah 💋 that’s the whole page, bestie. source is http://cppreference.com, version/date is 2024.06.10, and the page is std::make_tuple(3). go make some tuples and absolutely ate that template deduction. 💖✨