std::binary_function
<functional>
class Arg1,
class Arg2,
class Result
(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
first_argument_type
Arg1
second_argument_type
Arg2
result_type
Result
[edit] Example
#include <algorithm> #include <functional> #include <iostream> #include <vector> struct same : std::binary_function<int, int, bool> { bool operator()(int a, int b) const { return a == b; } }; int main() { std::vector <char> v1{'A', 'B', 'C', 'D', 'E'}; std::vector <char> v2{'E', 'D', 'C', 'B', 'A'}; std::vector <bool> 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
(class template) [edit]
(function template) [edit]
(class template) [edit]
(class template) [edit]