deduction guides for std::priority_queue

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C++
Containers library
std::priority_queue
Defined in header <queue>
template < class Comp, class Container >

priority_queue( Comp, Container )

- > priority_queue< typename Container:: value_type, Container, Comp> ;
(1) (since C++17)
template < class InputIt,

class Comp = std::less < /*iter-value-type*/ <InputIt>>,
class Container = std::vector < /*iter-value-type*/ <InputIt> >
priority_queue( InputIt, InputIt, Comp = Comp( ), Container = Container( ) )

- > priority_queue< /*iter-value-type*/ <InputIt>, Container, Comp> ;
(2) (since C++17)
template < class Comp, class Container, class Alloc >

priority_queue( Comp, Container, Alloc )

- > priority_queue< typename Container:: value_type, Container, Comp> ;
(3) (since C++17)
template < class InputIt, class Alloc >

priority_queue( InputIt, InputIt, Alloc )
- > priority_queue< /*iter-value-type*/ <InputIt>,
std::vector < /*iter-value-type*/ <InputIt>, Alloc>,

std::less < /*iter-value-type*/ <InputIt>>> ;
(4) (since C++17)
template < class InputIt, class Comp, class Alloc >

priority_queue( InputIt, InputIt, Comp, Alloc )
- > priority_queue< /*iter-value-type*/ <InputIt>,

std::vector < /*iter-value-type*/ <InputIt>, Alloc>, Comp> ;
(5) (since C++17)
template < class InputIt, class Comp, class Container, class Alloc >

priority_queue( InputIt, InputIt, Comp, Container, Alloc )

- > priority_queue< typename Container:: value_type, Container, Comp> ;
(6) (since C++17)
template < ranges::input_range R,

class Comp = std::less < ranges::range_value_t <R>> >
priority_queue( std::from_range_t, R&&, Comp = Comp( ) )
- > priority_queue< ranges::range_value_t <R>,

std::vector < ranges::range_value_t <R>>, Comp> ;
(7) (since C++23)
template < ranges::input_range R, class Comp, class Alloc >

priority_queue( std::from_range_t, R&&, Comp, Alloc )
- > priority_queue< ranges::range_value_t <R>,

std::vector < ranges::range_value_t <R>, Alloc>, Comp> ;
(8) (since C++23)
template < ranges::input_range R, class Alloc >

priority_queue( std::from_range_t, R&&, Alloc )
- > priority_queue< ranges::range_value_t <R>,

std::vector < ranges::range_value_t <R>, Alloc>> ;
(9) (since C++23)

The following deduction guides are provided for std::priority_queue

1-6) Allow deduction from underlying container type and from an iterator range. /*iter-value-type*/<It> denotes typename std::iterator_traits <It> :: value_type for any type It
7-9) Allow deduction from a std::from_range_t tag and an input_range

These overloads participate in overload resolution only if

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 { } )

Notes

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overloads (7-9)

Example

Run this code
#include <functional>
#include <iostream>
#include <queue>
#include <vector>
 
int main()
{
    const std::vector<int> v = {1, 2, 3, 4};
    std::priority_queue pq1{std::greater<int>{}, v}; // deduces std::priority_queue<
                                                     //     int, std::vector<int>,
                                                     //     std::greater<int>>
    for (; !pq1.empty(); pq1.pop())
        std::cout << pq1.top() << ' ';
    std::cout << '\n';
 
    std::priority_queue pq2{v.begin(), v.end()}; // deduces std::priority_queue<int>
 
    for (; !pq2.empty(); pq2.pop())
        std::cout << pq2.top() << ' ';
    std::cout << '\n';
}

Output: 

1 2 3 4
4 3 2 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 3506 C++17 deduction guides from iterator and allocator were missing added
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