理解函数对象的函数适配器

// leran.cpp : 定义控制台应用程序的入口点。

 

 

#include "stdafx.h"

#include<iostream>

#include <vector>

#include<algorithm>

#include<functional>

using namespace std;

class GT_cls

{

public:

GT_cls(size_t val = 0):bound(val){}

bool operator()(const string &s)

{

return  s.size()>=bound;

}

private:

std::string::size_type bound;

};

 

int _tmain(int argc, _TCHAR* argv[])

{

 

 

  int a[] = {1, 2, 3, 4, 5, 6, 7, 8};

  vector<int> ivec(a, a+8);

  size_t n1 = count_if(ivec.begin(), ivec.end(), bind2nd(less_equal<int>(), 5));

  cout << "n1:" << n1 << endl;

  //size_t n = count_if(ivec.begin(), ivec.end(), not1(bind2nd(less_equal<int>(), 5)));

  size_t n2 = count_if(ivec.begin(), ivec.end(), bind1st(less_equal<int>(), 5));

  cout << "n2:" << n2 << endl;

  less_equal<int> le;

  size_t n3 = le(5, 8);

  cout << "n3:" << n3 << endl;

 

  vector<int>::iterator ite = ivec.begin();

 

  while((ite = find_if(ite, ivec.end(), bind2nd(greater<int>(), 5))) != ivec.end())

  {

    cout << *ite << " ";

    ite++;

  }

  cout << endl;

 

  

  sort(ivec.begin(), ivec.end(), greater<int>());

 

  vector<int>::iterator ites = ivec.begin();

  while(ites!= ivec.end())

  {

    cout << *ites << " ";

    ites++;

  }

 

 

}

 

输出结果:

n1:5

n2:4

n3:1

6 7 8

8 7 6 5 4 3 2 1