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) (5) (since C++17)
   -> priority_queue</*iter-value-type*/<InputIt>,
   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>;
   These deduction guides are provided for std::priority_queue to 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.
   These overloads participate in overload resolution only if
     * InputIt satisfies LegacyInputIterator,
     * Comp does not satisfy Allocator,
     * Container does not satisfy Allocator,
     * for overloads (4) and (5),
       (since C++23) Alloc satisfies Allocator, and
     * for overloads (3) and (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.

Example
// Run this code
 #include <queue>
 #include <vector>
 #include <iostream>
 #include <functional>
 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