预定义函数对象

#include <iostream>    #include<string>    #include <vector>    #include <list>    #include <set>    #include <map>    #include <algorithm>    #include <functional>  using namespace std; //plus 预定义函数对象 能实现不能类型数据的+运算// 实现了算法和数据类型的分离 ===》通过函数对象技术实现的/*template<class _Ty>struct plus: public binary_function<_Ty, _Ty, _Ty>{// functor for operator+_Ty operator()(const _Ty& _Left, const _Ty& _Right) const{// apply operator+ to operandsreturn (_Left + _Right);}};*/void display(){plus<int> intadd;int x = 10l;int y = 200;int z = intadd(x,y);cout<<z<<endl;plus<string> stringadd;string s1 = "aaaa";string s2 = "bbbb";string s3 = stringadd(s1,s2);cout<<s3<<endl;cout<<"---------------"<<endl;/*template<class _RanIt,class _Pr> inlinevoid sort(_RanIt _First, _RanIt _Last, _Pr _Pred){// order [_First, _Last), using _Pred_DEBUG_RANGE(_First, _Last);_DEBUG_POINTER(_Pred);_Sort(_Unchecked(_First), _Unchecked(_Last), _Last - _First, _Pred);}*/vector<string> v;v.push_back("dddd");v.push_back("aaaa");v.push_back("cccc");v.push_back("cccc");v.push_back("bbbb");sort(v.begin(),v.end(),greater<string>());for (vector<string>::iterator it  = v.begin();it!=v.end();it++){cout<<*it<<endl;}//统计和字符串相等的个数//equal_to<string> 有两个参数 left参数来自容器，right参数来自sc；//bind2nd函数适配器 把预定义函数对象和第二个参数进行绑定string sc = "cccc";int num = count_if(v.begin(),v.end(),bind2nd(equal_to<string>(),sc));cout<<num<<endl;}int main(){display();system("pause");return 0;}