代码如下:

#include <iostream>
#include <string>
using namespace std;//函数对象在使用时，可以像普通函数那样调用，可以有参数，可以有返回值
class MyAdd
{
public:int operator()(int a, int b){return a + b;}
};void test01()
{MyAdd myAdd;cout << myAdd(10, 10) << endl;
}//函数对象可以有自己的状态
class MyPrint
{
public:MyPrint(){count = 0;}void operator()(string test){cout << test << endl;count++;}int count = 0;
};void test02()
{MyPrint myPrint;myPrint("hello world");myPrint("hello world");myPrint("hello world");cout << "count = " << myPrint.count << endl;}//函数对象可以作为参数传递
void doPrint(MyPrint &mp, string test)
{mp(test);
}void test03()
{MyPrint myPrint;doPrint(myPrint, "hello c++");
}int main()
{test01();test02();test03();return 0;
}

测试结果:

总结:

一元谓词
代码如下:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;struct GreaterFive {bool operator()(int a){return a > 5;}
};void test01()
{vector<int>v;for (int i = 0; i < 10; i++){v.push_back(i);}vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());if (it == v.end()){cout << "no find" << endl;}else{cout << "find" << *it << endl;}}int main()
{test01();return 0;
}

测试结果:

总结:

二元谓词
代码如下:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;class cmp
{
public:bool operator()(int a, int b){return a > b;}
};void test01()
{vector<int>v;v.push_back(10);v.push_back(40);v.push_back(20);v.push_back(30);v.push_back(50);sort(v.begin(), v.end());for (vector<int>::iterator it = v.begin(); it != v.end(); it++){cout << *it << " ";}cout << endl;cout << "---------------------------------------" << endl;sort(v.begin(), v.end(), cmp());for (vector<int>::iterator it = v.begin(); it != v.end(); it++){cout << *it << " ";}cout << endl;}int main() {test01();return 0;
}

测试结果:

总结:

代码如下:

#include <iostream>
#include <functional>
using namespace std;void test01()
{negate<int> n;cout << n(50) << endl;
}void test02()
{plus<int>p;cout << p(10, 20) << endl;
}int main()
{test01();test02();return 0;
}

测试结果:

总结:

代码如下:

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;class cmp
{
public:bool operator()(int a, int b){return a > b;}
};void test01()
{vector<int>v;v.push_back(10);v.push_back(20);v.push_back(50);v.push_back(40);v.push_back(90);v.push_back(70);for (vector<int>::iterator it = v.begin(); it != v.end(); it++){cout << *it << " ";}cout << endl;sort(v.begin(), v.end(), greater<int>());for (vector<int>::iterator it = v.begin(); it != v.end(); it++){cout << *it << " ";}cout << endl;}int main()
{test01();return 0;
}

测试结果:

总结:

代码如下:

#include <iostream>
#include <functional>
#include <vector>
#include <algorithm>
using namespace std;void test01()
{vector<bool> v;v.push_back(true);v.push_back(false);v.push_back(true);v.push_back(false);for (vector<bool>::iterator it = v.begin(); it != v.end(); it++){cout << *it << " ";}cout << endl;vector<bool> v2;v2.resize(v.size());transform(v.begin(), v.end(), v2.begin(), logical_not<bool>());for (vector<bool>::iterator it = v2.begin(); it != v2.end(); it++){cout << *it << " ";}cout << endl;}int main()
{test01();return 0;
}

测试结果:

总结: