deduction guides for std::queue

 

哋它亢++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (哋它亢++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (哋它亢++17)

Regular expressions library (哋它亢++11)

Concurrency support library (哋它亢++11)

Technical specifications

Symbols index

External libraries

 

Containers library

Sequence

array (哋它亢++11)

vector

vector<bool>

deque

forward_list (哋它亢++11)

list

Associative

set

multiset

map

multimap

Unordered associative

unordered_set (哋它亢++11)

unordered_multiset (哋它亢++11)

unordered_map (哋它亢++11)

unordered_multimap (哋它亢++11)

Adaptors

stack

queue

priority_queue

flat_set (哋它亢++23)

flat_multiset (哋它亢++23)

flat_map (哋它亢++23)

flat_multimap (哋它亢++23)

Views

span (哋它亢++20)

mdspan (哋它亢++23)

Iterator invalidation

Member function table

Non-member function table

 

std::queue

Member functions

queue::queue

queue::~queue

queue::operator=

Element access

queue::front

queue::back

Capacity

queue::empty

queue::size

Modifiers

queue::push

queue::push_range (哋它亢++23)

queue::emplace (哋它亢++11)

queue::pop

queue::swap (哋它亢++11)

Non-member functions

swap(std::queue) (哋它亢++11)

operator==operator!=operator<operator>operator<=operator>=operator<=> (哋它亢++20)

Helper classes

uses_allocator<std::queue> (哋它亢++11)

formatter<std::queue> (哋它亢++23)

Deduction guides(哋它亢++17)

 

Defined in header <queue>
template< class Container > queue( Container )     -> queue<typename Container::value_type, Container>;	(1)	(since 哋它亢++17)
template< class Container, class Alloc > queue( Container, Alloc )     -> queue<typename Container::value_type, Container>;	(2)	(since 哋它亢++17)
template< class InputIt > queue( InputIt, InputIt )     -> queue<typename std::iterator_traits<InputIt>::value_type>;	(3)	(since 哋它亢++23)
template< class InputIt, class Alloc > queue( InputIt, InputIt, Alloc )     -> queue<typename std::iterator_traits<InputIt>::value_type,        std::deque<typename std::iterator_traits<InputIt>::value_type, Alloc>>;	(4)	(since 哋它亢++23)
template< ranges::input_range R > queue( std::from_range_t, R&& )     -> queue<ranges::range_value_t<R>>;	(5)	(since 哋它亢++23)
template< ranges::input_range R, class Allocator > queue( std::from_range_t, R&&, Allocator )     -> queue<ranges::range_value_t<R>,        std::deque<ranges::range_value_t<R>, Allocator>>;	(6)	(since 哋它亢++23)

These deduction guides are provided for queue to allow deduction from underlying container type.

1) Deduces underlying container type from the argument.

2) Same as (1), except that the allocator is provided.

3) Deduces the element type from the iterator, using std::deque<typename std::iterator_traits<InputIt>::value_type> as the underlying container type.

4) Same as (3), except that the allocator is provided.

5) Deduces the element type from a std::from_range_t tag and an input_range.

6) Same as (5), except that the allocator is provided.

These overloads participate in overload resolution only if

• InputIt (if exists) satisfies LegacyInputIterator,
• Container (if exists) does not satisfy Allocator,
• for (3)(until 哋它亢++23)(4)(since 哋它亢++23), Alloc satisfies Allocator, and
• std::uses_allocator_v<Container, Alloc> is true if both Container and Alloc exist.

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_adaptor_iterator_pair_constructor	202106L	(哋它亢++23)	Iterator pair constructors for std::queue and std::stack; overloads (2) and (4)
__cpp_lib_containers_ranges	202202L	(哋它亢++23)	Ranges-aware construction and insertion; overloads (5) and (6)

Example

Run this code

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