deductiongu...string_view(3)

🎀 NAME 🎀

deductionguidesforstd::basic_string_view — deductionguidesforstd::basic_string_view

Okay so this is deductiongu...string_view(3) from the C++ Standard Libary manual — yes, “Libary” with the typo is literally what the header says, iykyk 💅. The NAME line is the same thing twice, and we are keeping it that way, periodt.

✨ Synopsis ✨

Defined in header <string_view>.

template< class It, class End >
basic_string_view( It, End ) ->
(1) (since C++20)
basic_string_view<std::iter_value_t<It>>;
template< class R >
basic_string_view( R&& ) ->
(2) (since C++23)
basic_string_view<ranges::range_value_t<R>>;

These deduction guides are provided for std::basic_string_view, bestie. Here’s the tea:

1. Guide (1), since C++20 — this deduction guide allows the character type to be deduced from the iterator-sentinel pair. This overload participates in overload resolution only if It satisfies contiguous_iterator and End satisfies sized_sentinel_for for It.
2. Guide (2), since C++23 — this deduction guide allows the character type to be deduced from the range. This overload participates in overload resolution only if R satisfies contiguous_range.

🌈 Example 🌈

The example literally tells you // Run this code, so run it, bestie:

// Run this code

#include <array>
#include <iostream>
#include <string_view>

int main()
{
    std::array a1{'n', 'u', 'c', 'l', 'e', 'o', 'n', 's', ':', '\n'};
    std::basic_string_view s1(a1.cbegin(), a1.cend()); // deduction: CharT -> char
    static_assert(std::is_same_v<decltype(s1)::value_type, char>);
    std::cout << s1;

    std::array a2{L'p', L'r', L'o', L't', L'o', L'n', L's', L'\n'};
    std::basic_string_view s2(a2.cbegin(), a2.cend()); // deduction: CharT -> wchar_t
    static_assert(std::is_same_v<decltype(s2)::value_type, wchar_t>);
    std::wcout << s2;

    std::array<long, 9> a3{'n', 'e', 'u', 't', 'r', 'o', 'n', 's', '\n'};
    std::basic_string_view s3(a3.cbegin(), a3.cend()); // deduction: CharT -> long
    static_assert(std::is_same_v<decltype(s3)::value_type, long>);
    for (const auto e : s3)
        std::cout << static_cast<char>(e);
}

💖 Output 💖

nucleons:
protons
neutrons

Cute sign-off 💖: source/version is http://cppreference.com, date is 2024.06.10, and the footer tag is deductiongu...string_view(3). Love that for us, bye 💅✨