deductionguidesforstd::priority_queue(3)

NAME
deductionguidesforstd::priority_queue - deductionguidesforstd::priority_queue

Synopsis
   Defined in header <queue>
   template< class Comp, class Container >
   priority_queue( Comp, Container ) (1) (since C++17)
       -> priority_queue<typename Container::value_type, Container,
   Comp>;
   template< class InputIt,
             class Comp = std::less</*iter-value-type*/<InputIt>>,
             class Container =
   std::vector</*iter-value-type*/<InputIt> > (2) (since C++17)
   priority_queue( InputIt, InputIt, Comp = Comp(), Container =
   Container() )
       -> priority_queue</*iter-value-type*/<InputIt>, Container,
   Comp>;
   template< class Comp, class Container, class Alloc >
   priority_queue( Comp, Container, Alloc ) (3) (since C++17)
       -> priority_queue<typename Container::value_type, Container,
   Comp>;
   template< class InputIt, class Alloc >
   priority_queue( InputIt, InputIt, Alloc )
       -> priority_queue</*iter-value-type*/<InputIt>, (4) (since C++17)
                        std::vector</*iter-value-type*/<InputIt>,
   Alloc>,
                        std::less</*iter-value-type*/<InputIt>>>;
   template< class InputIt, class Comp, class Alloc >
   priority_queue( InputIt, InputIt, Comp, Alloc )
       -> priority_queue</*iter-value-type*/<InputIt>, (5) (since C++17)
                        std::vector</*iter-value-type*/<InputIt>,
   Alloc>, Comp>;
   template< class InputIt, class Comp, class Container, class Alloc
   >
   priority_queue( InputIt, InputIt, Comp, Container, Alloc ) (6) (since C++17)
       -> priority_queue<typename Container::value_type, Container,
   Comp>;
   template< ranges::input_range R,
             class Comp = std::less<ranges::range_value_t<R>> >
   priority_queue( std::from_range_t, R&&, Comp = Comp() ) (7) (since C++23)
       -> priority_queue<ranges::range_value_t<R>,
                        std::vector<ranges::range_value_t<R>>,
   Comp>;
   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>, (8) (since C++23)
                        std::vector<ranges::range_value_t<R>,
   Alloc>, Comp>;
   template< ranges::input_range R, class Alloc >
   priority_queue( std::from_range_t, R&&, Alloc )
       -> priority_queue<ranges::range_value_t<R>, (9) (since C++23)
                        std::vector<ranges::range_value_t<R>,
   Alloc>>;
   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
     * InputIt satisfies LegacyInputIterator,
     * Comp does not satisfy Allocator,
     * Container does not satisfy Allocator,
     * for overloads (4,5),
       (since C++23) Alloc satisfies Allocator, and
     * for overloads (3,6), std::uses_allocator_v<Container, Alloc> is true.
   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;
                        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 added
                       were missing