Standard library header <stack>

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Standard library headers
 

This header is part of the containers library.

Includes

(C++20)
Three-way comparison operator support
std::initializer_list class template

Classes

adapts a container to provide stack (LIFO data structure)
(class template)
specializes the std::uses_allocator type trait
(class template specialization)

Functions

lexicographically compares the values of two stacks
(function template)
specializes the std::swap algorithm
(function template)

Synopsis

#include <compare>
#include <initializer_list>
 
namespace std {
  // class template stack
  template<class T, class Container = deque<T>>
  class stack;
 
  template<class T, class Container>
  bool operator==(const stack<T, Container>& x, const stack<T, Container>& y);
  template<class T, class Container>
  bool operator!=(const stack<T, Container>& x, const stack<T, Container>& y);
  template<class T, class Container>
  bool operator<(const stack<T, Container>& x, const stack<T, Container>& y);
  template<class T, class Container>
  bool operator>(const stack<T, Container>& x, const stack<T, Container>& y);
  template<class T, class Container>
  bool operator<=(const stack<T, Container>& x, const stack<T, Container>& y);
  template<class T, class Container>
  bool operator>=(const stack<T, Container>& x, const stack<T, Container>& y);
  template<class T, three_way_comparable Container>
  compare_three_way_result_t<Container> operator<=>(const stack<T, Container>& x,
                                                    const stack<T, Container>& y);
 
  template<class T, class Container>
  void swap(stack<T, Container>& x, stack<T, Container>& y) noexcept(noexcept(x.swap(y)));
  template<class T, class Container, class Alloc>
  struct uses_allocator<stack<T, Container>, Alloc>;
 
  // formatter specialization for stack
  template<class CharT, class T, formattable<CharT> Container>
  struct formatter<stack<T, Container>, CharT>;
}

Class template std::stack

namespace std {
  template<class T, class Container = deque<T>>
  class stack
  {
  public:
    using value_type      = typename Container::value_type;
    using reference       = typename Container::reference;
    using const_reference = typename Container::const_reference;
    using size_type       = typename Container::size_type;
    using container_type  = Container;
 
  protected:
    Container c;
 
  public:
    stack()
      : stack(Container())
    {
    }
    explicit stack(const Container&);
    explicit stack(Container&&);
    template<class InputIter>
    stack(InputIter first, InputIter last);
    template<container-compatible-range<T> R>
    stack(from_range_t, R&& rg);
    template<class Alloc>
    explicit stack(const Alloc&);
    template<class Alloc>
    stack(const Container&, const Alloc&);
    template<class Alloc>
    stack(Container&&, const Alloc&);
    template<class Alloc>
    stack(const stack&, const Alloc&);
    template<class Alloc>
    stack(stack&&, const Alloc&);
    template<class InputIter, class Alloc>
    stack(InputIter first, InputIter last, const Alloc&);
    template<container-compatible-range<T> R, class Alloc>
    stack(from_range_t, R&& rg, const Alloc&);
 
    bool empty() const { return c.empty(); }
    size_type size() const { return c.size(); }
    reference top() { return c.back(); }
    const_reference top() const { return c.back(); }
    void push(const value_type& x) { c.push_back(x); }
    void push(value_type&& x) { c.push_back(std::move(x)); }
    template<container-compatible-range<T> R>
    void push_range(R&& rg);
    template<class... Args>
    decltype(auto) emplace(Args&&... args)
    {
      return c.emplace_back(std::forward<Args>(args)...);
    }
    void pop() { c.pop_back(); }
    void swap(stack& s) noexcept(is_nothrow_swappable_v<Container>)
    {
      using std::swap;
      swap(c, s.c);
    }
  };
 
  template<class Container>
  stack(Container) -> stack<typename Container::value_type, Container>;
 
  template<class InputIter>
  stack(InputIter, InputIter) -> stack</*iter-value-type*/<InputIter>>;
 
  template<ranges::input_range R>
  stack(from_range_t, R&&) -> stack<ranges::range_value_t<R>>;
 
  template<class Container, class Allocator>
  stack(Container, Allocator) -> stack<typename Container::value_type, Container>;
 
  template<class InputIter, class Allocator>
  stack(InputIter, InputIter, Allocator)
    -> stack</*iter-value-type*/<InputIter>,
             deque</*iter-value-type*/<InputIter>, Allocator>>;
 
  template<ranges::input_range R, class Allocator>
  stack(from_range_t, R&&, Allocator)
    -> stack<ranges::range_value_t<R>, deque<ranges::range_value_t<R>, Allocator>>;
 
  template<class T, class Container, class Alloc>
  struct uses_allocator<stack<T, Container>, Alloc>
    : uses_allocator<Container, Alloc>::type
  {};
}