From cppreference.com
template<classArg1,classArg2,classResult>structbinary_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
, require the function objects they adapt to have certain types defined;
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.
Member types
Type Definition first_argument_typeArg1second_argument_typeArg2result_typeResultExample
Run this code
#include<algorithm>#include<functional>#include<iostream>#include<vector>structsame:std::binary_function<int,int,bool>{booloperator()(inta,intb)const{returna==b;}};intmain(){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_ti=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 See also
(C++11)
copyable wrapper of any copy constructible callable object
(class template)
(C++23)
move-only wrapper of any callable object that supports qualifiers in a given call signature
(class template)
(deprecated in C++11)(removed in C++17)
creates an adaptor-compatible function object wrapper from a pointer to function
(function template)
(deprecated in C++11)(removed in C++17)
adaptor-compatible wrapper for a pointer to binary function
(class template)
(deprecated in C++11)(removed in C++17)
adaptor-compatible unary function base class
(class template)