Any sequence container supporting operations
front(),
back(),
push_back()
and
pop_front()
can be used to instantiate
queue.
namespace std {
template<class T, class Container = deque<T>>
class queue {
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:
queue() : queue(Container()) {}
explicit queue(const Container&);
explicit queue(Container&&);
template<class Alloc> explicit queue(const Alloc&);
template<class Alloc> queue(const Container&, const Alloc&);
template<class Alloc> queue(Container&&, const Alloc&);
template<class Alloc> queue(const queue&, const Alloc&);
template<class Alloc> queue(queue&&, const Alloc&);
[[nodiscard]] bool empty() const { return c.empty(); }
size_type size() const { return c.size(); }
reference front() { return c.front(); }
const_reference front() const { return c.front(); }
reference back() { return c.back(); }
const_reference back() 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<class... Args>
decltype(auto) emplace(Args&&... args)
{ return c.emplace_back(std::forward<Args>(args)...); }
void pop() { c.pop_front(); }
void swap(queue& q) noexcept(is_nothrow_swappable_v<Container>)
{ using std::swap; swap(c, q.c); }
};
template<class Container>
queue(Container) -> queue<typename Container::value_type, Container>;
template<class Container, class Allocator>
queue(Container, Allocator) -> queue<typename Container::value_type, Container>;
template<class T, class Container>
void swap(queue<T, Container>& x, queue<T, Container>& y) noexcept(noexcept(x.swap(y)));
template<class T, class Container, class Alloc>
struct uses_allocator<queue<T, Container>, Alloc>
: uses_allocator<Container, Alloc>::type { };
}