NAME¶

deductionguidesforstd::queue - deductionguidesforstd::queue

Synopsis¶

Defined in header <queue>
template< class Container >

queue( Container ) (1) (since C++17)

-> queue<typename Container::value_type, Container>;
template< class Container, class Alloc >

queue( Container, Alloc ) (2) (since C++17)

-> queue<typename Container::value_type, Container>;
template< class InputIt >

queue( InputIt, InputIt ) (3) (since C++23)

-> queue<typename std::iterator_traits<InputIt>::value_type>;
template< class InputIt, class Alloc >

queue( InputIt, InputIt, Alloc )
-> queue<typename std::iterator_traits<InputIt>::value_type, (4) (since C++23)

std::deque<typename
std::iterator_traits<InputIt>::value_type, Alloc>>;
template< ranges::input_range R >

queue( std::from_range_t, R&& ) (5) (since C++23)

-> queue<ranges::range_value_t<R>>;
template< ranges::input_range R, class Allocator >

queue( std::from_range_t, R&&, Allocator ) (6) (since C++23)
-> queue<ranges::range_value_t<R>,

std::deque<ranges::range_value_t<R>, Allocator>>;

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 C++23)
(4)
(since C++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
Iterator pair
constructors for
__cpp_lib_adaptor_iterator_pair_constructor 202106L (C++23) std::queue and
std::stack; overloads
(2) and (4)
Ranges-aware
__cpp_lib_containers_ranges 202202L (C++23) 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>>
}