struct compare_three_way {
template<class T, class U>
requires three_way_comparable_with<T, U> || *BUILTIN-PTR-THREE-WAY*(T, U)
constexpr auto operator()(T&& t, U&& u) const;
using is_transparent = *unspecified*;
};

```
template<class T, class U>
requires three_way_comparable_with<T, U> ||
```*BUILTIN-PTR-THREE-WAY*(T, U)
constexpr auto operator()(T&& t, U&& u) const;

- If the expression std::forward<T>(t) <=> std::forward<U>(u) results in a call to a built-in operator <=> comparing pointers of type P, returns strong_ordering::less if (the converted value of) t precedes u in the implementation-defined strict total order over pointers ([defns.order.ptr]), strong_ordering::greater if u precedes t, and otherwise strong_ordering::equal.
- Otherwise, equivalent to: return std::forward<T>(t) <=> std::forward<U>(u);