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deductiongu...red_multimap(3) C++ Standard Libarydeductiongu...red_multimap(3) NAME deductionguidesforstd::unordered_multimap - deductionguidesforstd::un- ordered_multimap Synopsis Defined in header <unordered_map> template< class InputIt, class Hash = std::hash<iter_key_t<InputIt>>, class Pred = std::equal_to<iter_key_t<InputIt>>, class Alloc = std::allocator<iter_to_alloc_t<InputIt>> > unordered_multimap( InputIt, InputIt, typename /*see below*/::size_type = (1) (since C++17) /*see below*/, Hash = Hash(), Pred = Pred(), Alloc = Alloc() ) -> unordered_multimap<iter_key_t<InputIt>, iter_val_t<InputIt>, Hash, Pred, Alloc>; template< class Key, class T, class Hash = std::hash<Key>, class Pred = std::equal_to<Key>, class Alloc = std::allocator<std::pair<const Key, T>> > unordered_multimap( std::initializer_list<std::pair<Key, T>>, (2) (since C++17) typename /*see below*/::size_type = /*see below*/, Hash = Hash(), Pred = Pred(), Alloc = Alloc() ) -> unordered_multimap<Key, T, Hash, Pred, Alloc>; template< class InputIt, class Alloc > unordered_multimap( InputIt, InputIt, typename /*see below*/::size_type, Alloc ) -> unordered_multimap<iter_key_t<InputIt>, (3) (since C++17) iter_val_t<InputIt>, std::hash<iter_key_t<InputIt>>, std::equal_to<iter_key_t<InputIt>>, Alloc>; template< class InputIt, class Alloc > unordered_multimap( InputIt, InputIt, Alloc ) -> unordered_multimap<iter_key_t<InputIt>, iter_val_t<InputIt>, (4) (since C++17) std::hash<iter_key_t<InputIt>>, std::equal_to<iter_key_t<InputIt>>, Alloc>; template< class InputIt, class Hash, class Alloc > unordered_multimap( InputIt, InputIt, typename /*see below*/::size_type, Hash, Alloc ) -> unordered_multimap<iter_key_t<InputIt>, (5) (since C++17) iter_val_t<InputIt>, Hash, std::equal_to<iter_key_t<InputIt>>, Alloc>; template< class Key, class T, typename Alloc > unordered_multimap( std::initializer_list<std::pair<Key, T>>, typename /*see below*/::size_type, Alloc (6) (since C++17) ) -> unordered_multimap<Key, T, std::hash<Key>, std::equal_to<Key>, Alloc>; template< class Key, class T, typename Alloc > unordered_multimap( std::initializer_list<std::pair<Key, T>>, Alloc ) (7) (since C++17) -> unordered_multimap<Key, T, std::hash<Key>, std::equal_to<Key>, Alloc>; template< class Key, class T, class Hash, class Alloc > unordered_multimap( std::initializer_list<std::pair<Key, T>>, typename /*see below*/::size_type, Hash, (8) (since C++17) Alloc ) -> unordered_multimap<Key, T, Hash, std::equal_to<Key>, Alloc>; template< ranges::input_range R, class Hash = std::hash<range_key_t<R>>, class Pred = std::equal_to<range_key_t<R>>, class Alloc = std::allocator<range_to_alloc_t<R>> > unordered_multimap( std::from_range_t, R&&, (9) (since C++23) typename /* see description */::size_type = /* see description */, Hash = Hash(), Pred = Pred(), Alloc = Alloc() ) -> unordered_multimap<range_key_t<R>, range_mapped_t<R>, Hash, Pred, Alloc>; template< ranges::input_range R, class Alloc > unordered_multimap( std::from_range_t, R&&, typename /* see description */::size_type, Alloc ) (10) (since C++23) -> unordered_multimap<range_key_t<R>, range_mapped_t<R>, std::hash<range_key_t<R>>, std::equal_to<range_key_t<R>>, Alloc>; template< ranges::input_range R, class Alloc > unordered_multimap( std::from_range_t, R&&, Alloc ) -> unordered_multimap<range_key_t<R>, range_mapped_t<R>, (11) (since C++23) std::hash<range_key_t<R>>, std::equal_to<range_key_t<R>>, Alloc>; template< ranges::input_range R, class Hash, class Alloc > unordered_multimap( std::from_range_t, R&&, typename /* see description */::size_type, Hash, Alloc ) (12) (since C++23) -> unordered_multimap<range_key_t<R>, range_mapped_t<R>, Hash, std::equal_to<range_key_t<R>>, Alloc>; Exposition-only helper type aliases template< class InputIter > using iter_val_t = (exposition only*) typename std::iterator_traits<InputIter>::value_type; template< class InputIter > using iter_key_t = (exposition only*) std::remove_const_t< std::tuple_element_t<0, iter_val_t<InputIter>>>; template< class InputIter > using iter_mapped_t = (exposition only*) std::tuple_element_t<1, iter_val_t<InputIter>>; template< class InputIter > using iter_to_alloc_t = std::pair<std::add_const_t<tuple_element_t<0, (exposition only*) iter_val_t<InputIter>>>, std::tuple_element_t<1, iter_val_t<InputIter>>>; template< ranges::input_range Range > using range_key_t = (since C++23) (ex- position only*) std::remove_const_t<typename ranges::range_value_t<Range>::first_type>; template< ranges::input_range Range > (since C++23) using range_mapped_t = (exposition only*) typename ranges::range_value_t<Range>::second_type; template< ranges::input_range Range > using range_to_alloc_t = std::pair<std::add_const_t<typename (since C++23) ranges::range_value_t<Range>::first_type>, (exposition only*) typename ranges::range_value_t<Range>::second_type>; 1-8) These deduction guide are provided for unordered_multimap to allow deduction from an iterator range (overloads (1,3-5)) and std::initializer_list (overloads (2,6-8)). 9-12) These deduction guides are provided for unordered_multimap 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, neither Hash nor Pred satisfy Allocator, and Hash is not an integral type. Note: the extent to which the library determines that a type does not satisfy LegacyInputIterator is unspecified, except that as a minimum inte- gral types do not qualify as input iterators. Likewise, the extent to which it deter- mines 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. The size_type parameter type in these guides in an refers to the size_type member type of the type deduced by the deduction guide. Notes Feature-test macro Value Std Feature __cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construc- tion and insertion; overloads (9-12) Example // Run this code #include <unordered_map> int main() { // std::unordered_multimap m1 = {{"foo", 1}, {"bar", 2}}; // Error: braced-init-list has no type cannot // deduce pair<Key, T> from {"foo", 1} or {"bar", 2} std::unordered_multimap m1 = {std::pair{"foo", 2}, {"bar", 3}}; // guide #2 std::unordered_multimap m2(m1.begin(), m1.end()); // guide #1 } Defect reports The following behavior-changing defect reports were applied retroac- tively to previously published C++ standards. DR Applied to Behavior as published Correct behavior LWG 3025 C++17 initializer-list guides take use std::pair<Key, T> std::pair<const Key, T> http://cppreference.com 2024.06.10 deductiongu...red_multimap(3)
NAME | Synopsis | Notes | Example
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