# 23 General utilities library [utilities]

## 23.14 Function objects [function.objects]

### 23.14.6 Arithmetic operations [arithmetic.operations]

The library provides basic function object classes for all of the arithmetic operators in the language ([expr.mul], [expr.add]).

#### 23.14.6.1 Class template plus[arithmetic.operations.plus]

```template <class T = void> struct plus { constexpr T operator()(const T& x, const T& y) const; }; ```

```constexpr T operator()(const T& x, const T& y) const; ```

Returns: x + y.

```template <> struct plus<void> { template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) + std::forward<U>(u)); using is_transparent = unspecified; }; ```

```template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) + std::forward<U>(u)); ```

Returns: std​::​forward<T>(t) + std​::​forward<U>(u).

#### 23.14.6.2 Class template minus[arithmetic.operations.minus]

```template <class T = void> struct minus { constexpr T operator()(const T& x, const T& y) const; }; ```

```constexpr T operator()(const T& x, const T& y) const; ```

Returns: x - y.

```template <> struct minus<void> { template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) - std::forward<U>(u)); using is_transparent = unspecified; }; ```

```template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) - std::forward<U>(u)); ```

Returns: std​::​forward<T>(t) - std​::​forward<U>(u).

#### 23.14.6.3 Class template multiplies[arithmetic.operations.multiplies]

```template <class T = void> struct multiplies { constexpr T operator()(const T& x, const T& y) const; }; ```

```constexpr T operator()(const T& x, const T& y) const; ```

Returns: x * y.

```template <> struct multiplies<void> { template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) * std::forward<U>(u)); using is_transparent = unspecified; }; ```

```template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) * std::forward<U>(u)); ```

Returns: std​::​forward<T>(t) * std​::​forward<U>(u).

#### 23.14.6.4 Class template divides[arithmetic.operations.divides]

```template <class T = void> struct divides { constexpr T operator()(const T& x, const T& y) const; }; ```

```constexpr T operator()(const T& x, const T& y) const; ```

Returns: x / y.

```template <> struct divides<void> { template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) / std::forward<U>(u)); using is_transparent = unspecified; }; ```

```template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) / std::forward<U>(u)); ```

Returns: std​::​forward<T>(t) / std​::​forward<U>(u).

#### 23.14.6.5 Class template modulus[arithmetic.operations.modulus]

```template <class T = void> struct modulus { constexpr T operator()(const T& x, const T& y) const; }; ```

```constexpr T operator()(const T& x, const T& y) const; ```

Returns: x % y.

```template <> struct modulus<void> { template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) % std::forward<U>(u)); using is_transparent = unspecified; }; ```

```template <class T, class U> constexpr auto operator()(T&& t, U&& u) const -> decltype(std::forward<T>(t) % std::forward<U>(u)); ```

Returns: std​::​forward<T>(t) % std​::​forward<U>(u).

#### 23.14.6.6 Class template negate[arithmetic.operations.negate]

```template <class T = void> struct negate { constexpr T operator()(const T& x) const; }; ```

```constexpr T operator()(const T& x) const; ```

Returns: -x.

```template <> struct negate<void> { template <class T> constexpr auto operator()(T&& t) const -> decltype(-std::forward<T>(t)); using is_transparent = unspecified; }; ```

```template <class T> constexpr auto operator()(T&& t) const -> decltype(-std::forward<T>(t)); ```

Returns: -std​::​forward<T>(t).