23 General utilities library [utilities]

23.4 Pairs [pairs]

23.4.3 Specialized algorithms [pairs.spec]

template <class T1, class T2> constexpr bool operator==(const pair<T1, T2>& x, const pair<T1, T2>& y);

Returns: x.first == y.first && x.second == y.second.

template <class T1, class T2> constexpr bool operator<(const pair<T1, T2>& x, const pair<T1, T2>& y);

Returns: x.first < y.first || (!(y.first < x.first) && x.second < y.second).

template <class T1, class T2> constexpr bool operator!=(const pair<T1, T2>& x, const pair<T1, T2>& y);

Returns: !(x == y).

template <class T1, class T2> constexpr bool operator>(const pair<T1, T2>& x, const pair<T1, T2>& y);

Returns: y < x.

template <class T1, class T2> constexpr bool operator>=(const pair<T1, T2>& x, const pair<T1, T2>& y);

Returns: !(x < y).

template <class T1, class T2> constexpr bool operator<=(const pair<T1, T2>& x, const pair<T1, T2>& y);

Returns: !(y < x).

template<class T1, class T2> void swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));

Effects: As if by x.swap(y).

Remarks: This function shall not participate in overload resolution unless is_swappable_v<T1> is true and is_swappable_v<T2> is true.

template <class T1, class T2> constexpr pair<V1, V2> make_pair(T1&& x, T2&& y);

Returns: pair<V1, V2>(std::forward<T1>(x), std::forward<T2>(y)), where V1 and V2 are determined as follows: Let Ui be decay_t<Ti> for each Ti. If Ui is a specialization of reference_wrapper, then Vi is Ui::type&, otherwise Vi is Ui.

[ Example: In place of:

  return pair<int, double>(5, 3.1415926);   // explicit types

a C++ program may contain:

  return make_pair(5, 3.1415926);           // types are deduced

— end example ]