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std::equal_to

Defined in header <functional> 
template< class T >
struct equal_to;
 (until C++14) 
template< class T = void >
struct equal_to;
 (since C++14)

Function object for performing comparisons. Unless specialised, invokes operator== on type T.

Specializations

The standard library provides a specialization of std::equal_to when T is not specified, which leaves the parameter types and return type to be deduced.

(C++14)
function object implementing x == y deducing argument and return types
(class template specialization)
(since C++14)

Member types

Type Definition
result_type (deprecated in C++17)(removed in C++20) bool
first_argument_type (deprecated in C++17)(removed in C++20) T
second_argument_type (deprecated in C++17)(removed in C++20) T

These member types are obtained via publicly inheriting std::binary_function<T, T, bool>.

 (until C++11)

Member functions

operator()
checks if the arguments are equal
(public member function)

std::equal_to::operator()

bool operator()( const T& lhs, const T& rhs ) const;
 (until C++14) 
constexpr bool operator()( const T& lhs, const T& rhs ) const;
 (since C++14)

Checks whether lhs is equal to rhs.

Parameters

lhs, rhs - values to compare

Return value

true if lhs == rhs, false otherwise.

Exceptions

May throw implementation-defined exceptions.

Possible implementation

constexpr bool operator()(const T& lhs, const T& rhs) const 
{
    return lhs == rhs;
}

See also

determines if two sets of elements are the same
(function template)
function object implementing x != y
(class template)
function object implementing x < y
(class template)
(C++20)
function object implementing x == y
(class)

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https://en.cppreference.com/w/cpp/utility/functional/equal_to