C++模板与STL【函数对象】

#include <string>
//1、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 v1,int v2)
  {
    return v1 + v2;
  }
};
void test01()
{
  MyAdd myAdd;
  cout << myAdd(10, 10) << endl;
}
//2、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++; //统计使用次数
  }
  int count; //内部自己的状态
};
void test02()
{
  MyPrint myPrint;
  myPrint("hello world");
  myPrint("hello world");
  myPrint("hello world");
  cout << "myPrint调用次数为： " << myPrint.count << endl;
}
//3、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();
  system("pause");
  return 0;
}

#include <vector>
#include <algorithm>
//1.一元谓词
struct GreaterFive{
  bool operator()(int val) {
    return val > 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 << "没找到!" << endl;
  }
  else {
    cout << "找到:" << *it << endl;
  }
}
int main() {
  test01();
  system("pause");
  return 0;
}

#include <vector>
#include <algorithm>
//二元谓词
class MyCompare
{
public:
  bool operator()(int num1, int num2)
  {
    return num1 > num2;
  }
};
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);
  //默认从小到大
  sort(v.begin(), v.end());
  for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
  {
    cout << *it << " ";
  }
  cout << endl;
  cout << "----------------------------" << endl;
  //使用函数对象改变算法策略，排序从大到小
  sort(v.begin(), v.end(), MyCompare());
  for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
  {
    cout << *it << " ";
  }
  cout << endl;
}
int main() {
  test01();
  system("pause");
  return 0;
}

#include <functional>
//negate
void test01()
{
  negate<int> n;
  cout << n(50) << endl;
}
//plus
void test02()
{
  plus<int> p;
  cout << p(10, 20) << endl;
}
int main() {
  test01();
  test02();
  system("pause");
  return 0;
}

#include <functional>
#include <vector>
#include <algorithm>
class MyCompare
{
public:
  bool operator()(int v1,int v2)
  {
    return v1 > v2;
  }
};
void test01()
{
  vector<int> v;
  v.push_back(10);
  v.push_back(30);
  v.push_back(50);
  v.push_back(40);
  v.push_back(20);
  for (vector<int>::iterator it = v.begin(); it != v.end(); it++) {
    cout << *it << " ";
  }
  cout << endl;
  //自己实现仿函数
  //sort(v.begin(), v.end(), MyCompare());
  //STL内建仿函数  大于仿函数
  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();
  system("pause");
  return 0;
}

#include <vector>
#include <functional>
#include <algorithm>
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;
  //逻辑非  将v容器搬运到v2中，并执行逻辑非运算
  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();
  system("pause");
  return 0;
}