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# std::equal_to<void>

From cppreference.com
< cpp‎ | utility‎ | functional

Defined in header `<functional>` |  |
template<> class equal_to<void>; |  | (since C++14)

std::equal_to<> is a specialization of std::equal_to with parameter and return type deduced.

### [edit] Member types

Member type | Definition
`is_transparent` | /* unspecified */

### [edit] Member functions

operator() | tests if the two arguments compare equal (public member function)

## std::equal_to<>::operator()

template< class T, class U> constexpr auto operator()( T&& lhs, U&& rhs ) const -> decltype(std::forward<T>(lhs) == std::forward<U>(rhs)); |  |

Returns the result of equality comparison between `lhs` and `rhs`.

### Parameters

lhs, rhs | - | values to compare

### Return value

The result of std::forward<T>(lhs) == std::forward<U>(rhs).

### [edit] Notes

The member type `is_transparent` indicates to the caller that this function object is a transparent function object: it accepts arguments of arbitrary types and uses perfect forwarding, which avoids unnecessary copying and conversion when the function object is used in heterogeneous context, or with rvalue arguments. In particular, template functions such as std::set::find and std::set::lower_bound make use of this member type on their `Compare` types.

### [edit] Example

| This section is incomplete Reason: no example

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