deduction guides for std::multimap
From cppreference.com
| 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>,
multimap std::less</*range-key-t*/<R>>, Alloc>;
|
(6) | (since C++23) |
| Exposition-only helper type aliases |
||
template< class InputIt >
using /*iter-val-t*/ =
typename std::iterator_traits<InputIt>::value_type;
|
(exposition only*) | |
template< class InputIt >
using /*iter-key-t*/ =
std::remove_const_t< std::tuple_element_t<0, /*iter-val-t*/<InputIt>>>;
|
(exposition only*) | |
template< class InputIt >
using /*iter-mapped-t*/ =
std::tuple_element_t<1, /*iter-val-t*/<InputIt>>;
|
(exposition only*) | |
template< class InputIt >
using /*iter-to-alloc-t*/ =
std::pair<std::add_const_t<tuple_element_t<0, /*iter-val-t*/<InputIt>>>,
std::tuple_element_t<1, /*iter-val-t*/<InputIt>>>;
|
(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 (2,4) take std::pair<const Key, T>
|
use std::pair<Key, T>
|
