20 General utilities library [utilities]

20.14 Function objects [function.objects]

20.14.9 Concept-constrained comparisons [range.cmp]

struct ranges::equal_to { template<class T, class U> constexpr bool operator()(T&& t, U&& u) const; using is_transparent = unspecified; };
template<class T, class U> constexpr bool operator()(T&& t, U&& u) const;
Constraints: T and U satisfy equality_­comparable_­with.
Preconditions: 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, the conversion sequences from both T and U to P are equality-preserving ([concepts.equality]); otherwise, T and U model equality_­comparable_­with.
Effects:
  • If the expression std​::​forward<T>(t) == std​::​forward<U>(u) results in a call to a built-in operator == comparing pointers: returns false if either (the converted value of) t precedes u or u precedes t in the implementation-defined strict total order over pointers ([defns.order.ptr]) and otherwise true.
  • Otherwise, equivalent to: return std​::​forward<T>(t) == std​::​forward<U>(u);
struct ranges::not_equal_to { template<class T, class U> constexpr bool operator()(T&& t, U&& u) const; using is_transparent = unspecified; };
template<class T, class U> constexpr bool operator()(T&& t, U&& u) const;
Constraints: T and U satisfy equality_­comparable_­with.
Effects: Equivalent to: return !ranges::equal_to{}(std::forward<T>(t), std::forward<U>(u));
struct ranges::greater { template<class T, class U> constexpr bool operator()(T&& t, U&& u) const; using is_transparent = unspecified; };
template<class T, class U> constexpr bool operator()(T&& t, U&& u) const;
Constraints: T and U satisfy totally_­ordered_­with.
Effects: Equivalent to: return ranges::less{}(std::forward<U>(u), std::forward<T>(t));
struct ranges::less { template<class T, class U> constexpr bool operator()(T&& t, U&& u) const; using is_transparent = unspecified; };
template<class T, class U> constexpr bool operator()(T&& t, U&& u) const;
Constraints: T and U satisfy totally_­ordered_­with.
Preconditions: 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, the conversion sequences from both T and U to P are equality-preserving ([concepts.equality]); otherwise, T and U model totally_­ordered_­with.
For any expressions ET and EU such that decltype((ET)) is T and decltype((EU)) is U, exactly one of ranges​::​less{}(ET, EU), ranges​::​less{}(EU, ET), or ranges​::​equal_­to{}(ET, EU) is true.
Effects:
  • If the expression std​::​forward<T>(t) < std​::​forward<U>(u) results in a call to a built-in operator < comparing pointers: returns true if (the converted value of) t precedes u in the implementation-defined strict total order over pointers ([defns.order.ptr]) and otherwise false.
  • Otherwise, equivalent to: return std​::​forward<T>(t) < std​::​forward<U>(u);
struct ranges::greater_equal { template<class T, class U> constexpr bool operator()(T&& t, U&& u) const; using is_transparent = unspecified; };
template<class T, class U> constexpr bool operator()(T&& t, U&& u) const;
Constraints: T and U satisfy totally_­ordered_­with.
Effects: Equivalent to: return !ranges::less{}(std::forward<T>(t), std::forward<U>(u));
struct ranges::less_equal { template<class T, class U> constexpr bool operator()(T&& t, U&& u) const; using is_transparent = unspecified; };
template<class T, class U> constexpr bool operator()(T&& t, U&& u) const;
Constraints: T and U satisfy totally_­ordered_­with.
Effects: Equivalent to: return !ranges::less{}(std::forward<U>(u), std::forward<T>(t));