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

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

Some standard library function object adaptors, such asstd::not2, require the function objects they adapt to have certain types defined;std::not2 requires the function object being adapted to have two types namedfirst_argument_type andsecond_argument_type. Deriving function objects that take two arguments fromstd::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 <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';}

A != E : trueB != D : trueC != C : falseD != B : trueE != A : true

[edit]See also

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