std::binary_function - cppreference.com (original) (raw)

| | | | | -------------------------------------------------------------------------- | | ---------------------------------------- | | template< class Arg1, class Arg2, class Result > struct binary_function; | | (deprecated in C++11) (removed in C++17) |

std::binary_function is a base class for creating function objects with two arguments.

std::binary_function does not define operator(); it is expected that derived classes will define this. std::binary_function provides only three types - first_argument_type, second_argument_type and result_type - defined by the template parameters.

Some standard library function object adaptors, such as std::not2, require the function objects they adapt to have certain types defined; std::not2 requires the function object being adapted to have two types named first_argument_type and second_argument_type. Deriving function objects that take two arguments from std::binary_function is an easy way to make them compatible with those adaptors.

std::binary_function is deprecated in C++11 and removed in C++17.

[edit] Member types

[edit] Example

#include #include #include #include   struct same : std::binary_function<int, int, bool> { bool operator()(int a, int b) const { return a == b; } };   int main() { std::vector v1{'A', 'B', 'C', 'D', 'E'}; std::vector v2{'E', 'D', 'C', 'B', 'A'}; std::vector v3(v1.size());   std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(same()));   std::cout << std::boolalpha; for (std::size_t i = 0; i < v1.size(); ++i) std::cout << v1[i] << " != " << v2[i] << " : " << v3[i] << '\n'; }

Output:

A != E : true B != D : true C != C : false D != B : true E != A : true

[edit] See also

| | copyable wrapper of any copy constructible callable object (class template) [edit] | | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | move-only wrapper of any callable object that supports qualifiers in a given call signature (class template) [edit] | | | (deprecated in C++11)(removed in C++17) | creates an adaptor-compatible function object wrapper from a pointer to function (function template) [edit] | | (deprecated in C++11)(removed in C++17) | adaptor-compatible wrapper for a pointer to binary function (class template) [edit] | | (deprecated in C++11)(removed in C++17) | adaptor-compatible unary function base class (class template) [edit] |