《Essential C++》系列笔记之第四章(基于对象的编程风格)之第九节(实现一个function object)

代码实践

• main.cpp

  #include 
  using namespace std;
  #include "LessThan.h"
  #include 
  
  int main()
  {
  	int a[] = { 34,5,234,65,32,756,2,34 };
  	vector<int> ivec(a, a + sizeof(a) / sizeof(int));
  
  	cout << count_less_than(ivec, 100) << endl;
  
  	print_less_than(ivec, 100);
  	cout << endl;
  
  	system("pause");
  	return 0;
  }
  

• LessThan.h

  #pragma once
  #include 
  #include 
  #include 
  using namespace std;
  
  class LessThan
  {
  public:
  	LessThan(int val)  //设置一个基值
  		:_val(val)
  	{}
  	bool operator()(int) const;
  private:
  	int _val;
  };
  
  int count_less_than(const vector<int>& ivec, int comp);
  
  void print_less_than(const vector<int>& ivec, int comp);
  

• LessThan.cpp

  #include "LessThan.h"
  
  inline bool LessThan::operator()(int val) const
  {
  	return (val < this->_val);
  }
  
  int count_less_than(const vector<int>& ivec, int comp)
  {
  	int count = 0;
  	LessThan lt(comp);
  
  	for (int i = 0; i < ivec.size(); i++)
  		if (lt(ivec[i]))
  			++count;
  
  	return count;
  }
  
  void print_less_than(const vector<int>& ivec, int comp)
  {
  	vector<int>::const_iterator iter = ivec.begin();
  	vector<int>::const_iterator it_end = ivec.end();
  
  	LessThan lt(comp);
  
  	while ((iter = find_if(iter, it_end, lt)) != it_end)
  	{
  		cout << *iter << " ";
  		++iter;
  	}
  }
  

今天是20200326 慕课好像看不完了