deduction guides for std::queue

Since C++17

Header: <queue>

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

# Declarations

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

(since C++17)

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

(since C++17)

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

(since C++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>>;

(since C++23)

template< ranges::input_range R >
queue( std::from_range_t, R&& )
-> queue<ranges::range_value_t<R>>;

(since C++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>>;

(since C++23)

# Notes

Feature-test macro Value Std Feature __cpp_lib_adaptor_iterator_pair_constructor 202106L (C++23) Iterator pair constructors for std::queue and std::stack; overloads (2) and (4) __cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overloads (5) and (6)

# Example

#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>>
}