equal_to

Library:  General utilities

Does not inherit

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A binary function object that returns true if its first argument equals its second

#include <functional>

namespace std {
  template <class T>
  struct equal_to;
}

equal_to is a binary function object. Its operator() returns true if x is equal to y. You can pass an equal_to object to any algorithm that requires a binary function. For example, the find_if() algorithm finds the first occurrence of any value from one sequence in another sequence as determined by applying a binary comparison operation. equal_to would be used in that algorithm in the following manner:

vector<int> vec1;
vector<int> vec2;
vector<int>::iterator iter1;
.
.
.
iter1 = find_if(vec1.begin(), vec1.end(),
                vec2.begin(), vec2.end(), equal_to<int>());

After this call to find_if(), iter1 points to the first element in vec1 for which equal_to(vec1[n],vec2[n]) returned true; or, if there were no matches, iter1 points to vec2.end().

namespace std {
  template <class T>
  struct equal_to : binary_function<T, T, bool> { 
    bool operator()(const T& x, const T& y) const;
  }; 
}

binary_function, Function Objects

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 20.3.3