# 22 General utilities library [utilities]

## 22.3 Pairs [pairs]

### 22.3.3 Specialized algorithms [pairs.spec]

```template<class T1, class T2, class U1, class U2> constexpr bool operator==(const pair<T1, T2>& x, const pair<U1, U2>& y); ```
Constraints: x.first == y.first and x.second == y.second are valid expressions and each of decltype(x.first == y.first) and decltype(x.second == y.second) models boolean-
testable
.
Returns: x.first == y.first && x.second == y.second.
```template<class T1, class T2, class U1, class U2> constexpr common_comparison_category_t<synth-three-way-result<T1, U1>, synth-three-way-result<T2, U2>> operator<=>(const pair<T1, T2>& x, const pair<U1, U2>& y); ```
Effects: Equivalent to: if (auto c = synth-three-way(x.first, y.first); c != 0) return c; return synth-three-way(x.second, y.second);
```template<class T1, class T2> constexpr void swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y))); template<class T1, class T2> constexpr void swap(const pair<T1, T2>& x, const pair<T1, T2>& y) noexcept(noexcept(x.swap(y))); ```
Constraints:
• For the first overload, is_swappable_v<T1> is true and is_swappable_v<T2> is true.
• For the second overload, is_swappable_v<const T1> is true and is_swappable_v<const T2> is true.
Effects: Equivalent to x.swap(y).
```template<class T1, class T2> constexpr pair<unwrap_ref_decay_t<T1>, unwrap_ref_decay_t<T2>> make_pair(T1&& x, T2&& y); ```
Returns: pair<unwrap_ref_decay_t<T1>, unwrap_ref_decay_t<T2>>(std::forward<T1>(x), std::forward<T2>(y))
[Example 1:
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
â€” end example]