deduction guides for std::multimap

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (C++11)

vector

vector<bool>

inplace_vector (C++26)

deque

forward_list (C++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (C++11)

unordered_multiset (C++11)

unordered_map (C++11)

unordered_multimap (C++11)

Adaptors

stack

queue

priority_queue

flat_set (C++23)

flat_multiset (C++23)

flat_map (C++23)

flat_multimap (C++23)

Views

span (C++20)

mdspan (C++23)

Tables

Iterator invalidation

Member function table

Non-member function table

 

std::multimap

Member functions

multimap::multimap multimap::~multimap        multimap::operator= multimap::get_allocator

Iterators multimap::beginmultimap::cbegin (C++11) multimap::endmultimap::cend (C++11) multimap::rbeginmultimap::crbegin (C++11)    multimap::rendmultimap::crend (C++11) Capacity multimap::size multimap::max_size multimap::empty Observers multimap::key_comp multimap::value_comp Modifiers multimap::clear multimap::insert multimap::erase multimap::swap multimap::merge (C++17) multimap::insert_range (C++23) multimap::emplace (C++11) multimap::emplace_hint (C++11) multimap::extract (C++17) Lookup multimap::count multimap::find multimap::contains (C++20) multimap::equal_range multimap::lower_bound multimap::upper_bound

Non-member functions

operator==operator<=> (C++20) std::swap(std::multimap) erase_if(std::multimap) (C++20)   operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)

Deduction guides(C++17)

 

Defined in header <map>
template< class InputIt,           class Comp = std::less<iter_key_t<InputIt>>,           class Alloc = std::allocator<iter_to_alloc_t<InputIt>> > multimap( InputIt, InputIt, Comp = Comp(), Alloc = Alloc() )     -> multimap<iter_key_t<InputIt>, iter_val_t<InputIt>, Comp, Alloc>;	(1)	(since C++17)
template< class Key,           class T,           class Comp = std::less<Key>,           class Alloc = std::allocator<std::pair<const Key, T>> > multimap( std::initializer_list<std::pair<Key, T>>, Comp = Comp(), Alloc = Alloc() )     -> multimap<Key, T, Comp, Alloc>;	(2)	(since C++17)
template< class InputIt, class Alloc > multimap( InputIt, InputIt, Alloc )     -> multimap<iter_key_t<InputIt>, iter_val_t<InputIt>,                 std::less<iter_key_t<InputIt>>, Alloc>;	(3)	(since C++17)
template< class Key, class T, class Alloc > multimap( std::initializer_list<std::pair<Key, T>>, Alloc )     -> multimap<Key, T, std::less<Key>, Alloc>;	(4)	(since C++17)
template< ranges::input_range R, class Compare = std::less<range_key_t<R>,           class Alloc = std::allocator<range_to_alloc_t<R>> > multimap( std::from_range_t, R&&, Compare = Compare(), Alloc = Alloc() )     -> multimap<range_key_t<R>, range_mapped_t<R>, Compare, Alloc>;	(5)	(since C++23)
template< ranges::input_range R, class Alloc > multimap( std::from_range_t, R&&, Alloc )     -> multimap<range_key_t<R>, range_mapped_t<R>, std::less<range_key_t<R>>, Alloc>;	(6)	(since C++23)
Exposition-only helper type aliases
template< class InputIter > using iter_val_t =     typename std::iterator_traits<InputIter>::value_type;		(exposition only*)
template< class InputIter > using iter_key_t =     std::remove_const_t< std::tuple_element_t<0, iter_val_t<InputIter>>>;		(exposition only*)
template< class InputIter > using iter_mapped_t =     std::tuple_element_t<1, iter_val_t<InputIter>>;		(exposition only*)
template< class InputIter > using iter_to_alloc_t =     std::pair<std::add_const_t<tuple_element_t<0, iter_val_t<InputIter>>>,               std::tuple_element_t<1, iter_val_t<InputIter>>>;		(exposition only*)
template< ranges::input_range Range > using range_key_t =     std::remove_const_t<typename ranges::range_value_t<Range>::first_type>;		(since C++23) (exposition only*)
template< ranges::input_range Range > using range_mapped_t =     typename ranges::range_value_t<Range>::second_type;		(since C++23) (exposition only*)
template< ranges::input_range Range > using range_to_alloc_t =     std::pair<std::add_const_t<typename ranges::range_value_t<Range>::first_type>,               typename ranges::range_value_t<Range>::second_type>;		(since C++23) (exposition only*)

1-4) These deduction guides are provided for multimap 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 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, and Comp does not satisfy Allocator.

Note: 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.

Notes

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

Example

Run this code

#include <map>
 
int main()
{
    // std::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::multimap m1 = {std::pair{"foo", 2}, {"bar", 3}}; // guide #2
    std::multimap m2(m1.begin(), m1.end()); // guide #1
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 3025	C++17	initializer-list guides take std::pair<const Key, T>	use std::pair<Key, T>