class template
<functional>
std::binary_function
template <class Arg1, class Arg2, class Result> struct binary_function;
template <class Arg1, class Arg2, class Result> struct binary_function; // deprecated
Binary function object base class
Note: This class has been deprecated in C++11.
This is a base class for standard binary function objects.
Generically, function objects are instances of a class with member function operator() defined. This member function allows the object to be used with the same syntax as a regular function call, and therefore its type can be used as template parameter when a generic function type is expected.
In the case of binary function objects, this operator() member function takes two parameters.
binary_function is just a base class, from which specific binary function objects are derived. It has no operator() member defined (which derived classes are expected to define) - it simply has three public data members that are typedefs of the template parameters. It is defined as:
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| template <class Arg1, class Arg2, class Result> struct binary_function { typedef Arg1 first_argument_type; typedef Arg2 second_argument_type; typedef Result result_type; };
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Members
| member type | definition | notes |
|---|
| first_argument_type | The first template parameter (Arg1) | Type of the first argument in member operator() |
| second_argument_type | The second template parameter (Arg2) | Type of the second argument in member operator() |
| return_type | The third template parameter (Result) | Type returned by member operator() |
Example
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| // binary_function example #include <iostream> // std::cout, std::cin #include <functional> // std::binary_function struct Compare : public std::binary_function<int,int,bool> { bool operator() (int a, int b) {return (a==b);} }; int main () { Compare Compare_object; Compare::first_argument_type input1; Compare::second_argument_type input2; Compare::result_type result; std::cout << "Please enter first number: "; std::cin >> input1; std::cout << "Please enter second number: "; std::cin >> input2; result = Compare_object (input1,input2); std::cout << "Numbers " << input1 << " and " << input2; if (result) std::cout << " are equal.\n"; else std::cout << " are not equal.\n"; return 0; }
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Possible output:
Please enter first number: 2 Please enter second number: 33 Numbers 2 and 33 are not equal. |
See also
- unary_function
- Unary function object base class (class template)