deductiongu...td::multiset(3)

💖 NAME 💖

deductionguidesforstd::multiset — literally deductionguidesforstd::multiset, that’s the name, bestie 🎀

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🦋 Synopsis 🦋

Hiii okay so this whole page lives in the C++ Standard Libary (that’s the header’s spelling, not mine 👀), and it’s all about deduction guides for std::multiset. Defined in header <set>:

Overload (1) — (since C++17)

template<
    class InputIt,
    class Comp = std::less<typename std::iterator_traits<InputIt>::value_type>,
    class Alloc = std::allocator<typename std::iterator_traits<InputIt>::value_type>>
multiset( InputIt, InputIt, Comp = Comp(), Alloc = Alloc() )
    -> multiset<typename std::iterator_traits<InputIt>::value_type, Comp, Alloc>;

Overload (2) — (since C++17)

template<
    class Key, class Comp = std::less<Key>,
    class Alloc = std::allocator<Key> >
multiset( std::initializer_list<Key>, Comp = Comp(), Alloc = Alloc() )
    -> multiset<Key, Comp, Alloc>;

Overload (3) — (since C++17)

template< class InputIt, class Alloc >
multiset( InputIt, InputIt, Alloc )
    -> multiset<typename std::iterator_traits<InputIt>::value_type,
                std::less<typename std::iterator_traits<InputIt>::value_type>, Alloc>;

Overload (4) — (since C++17)

template< class Key, class Alloc >
multiset( std::initializer_list<Key>, Alloc )
    -> multiset<Key, std::less<Key>, Alloc>;

Overload (5) — (since C++23)

template< ranges::input_range R, class Compare = less<ranges::range_value_t<R>>,
          class Alloc = std::allocator<ranges::range_value_t<R>> >
multiset( std::from_range_t, R&&, Compare = Compare(), Alloc = Alloc() )
    -> multiset<ranges::range_value_t<R>, Compare, Alloc>;

Overload (6) — (since C++23)

template< ranges::input_range R, class Alloc >
multiset( std::from_range_t, R&&, Alloc )
    -> multiset<ranges::range_value_t<R>,
                std::less<ranges::range_value_t<R>>, Alloc>;

1-4) These deduction guides are provided for multiset to allow deduction from an iterator range (overloads (1,3)) and std::initializer_list (overloads (2,4)).

5,6) These deduction guides are provided for multiset to allow deduction from a std::from_range_t tag and an input_range.

These overloads participate in overload resolution only if InputIt satisfies LegacyInputIterator, Alloc satisfies Allocator, and Comp does not satisfy Allocator.

Note, bestie: the extent to which the library determines that a type does not satisfy LegacyInputIterator is unspecified, except that as a minimum integral types do not qualify as input iterators. Likewise, the extent to which it determines that a type does not satisfy Allocator is unspecified, except that as a minimum the member type Alloc::value_type must exist and the expression std::declval<Alloc&>().allocate(std::size_t{}) must be well-formed when treated as an unevaluated operand. Unspecified is giving “we’re not gonna pin that down” energy 💅

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📝 Notes 📝

Feature-test macro vibes ✨:

• Feature-test macro: __cpp_lib_containers_ranges
• Value: 202202L
• Std: (C++23)
• Feature: Ranges-aware construction and insertion; overload (5,6)

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🌸 Example 🌸

// Run this code

#include <set>

int main()
{
    // guide #2 deduces std::multiset<int>
    std::multiset s = {1, 2, 3, 4};

    // guide #1 deduces std::multiset<int>
    std::multiset s2(s.begin(), s.end());
}

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okay that’s the whole vibe, bestie 💅✨ — source/version: http://cppreference.com, date: 2024.06.10, and the footer manual name is deductiongu...td::multiset(3). mwah 😽🫶