使用一个函数对象来保存状态

[c++]代码库

// 使用一个函数对象来保存状态
#include <algorithm>
#include <iostream>
#include <vector>
#include <list>

using namespace std;

template<typename elementType>
struct DisplayElementKeepCount {
	// Hold the count in a member variable
	int m_nCount;

	// Constructor
	DisplayElementKeepCount() {
		m_nCount = 0;
	}

	// Display the element, hold count!
	void operator ()(const elementType& element) {
		++m_nCount;
		cout << element << ' ';
	}
};

int main() {
	vector<int> vecIntegers;

	for (int nCount = 0; nCount < 10; ++nCount)
		vecIntegers.push_back(nCount);

	cout << "Displaying the vector of integers: " << endl;

	// Display the array of integers
	DisplayElementKeepCount<int> mResult;
	mResult = for_each(vecIntegers.begin() // Start of range
			, vecIntegers.end() // End of range
			, DisplayElementKeepCount<int>()); // function object

	cout << endl << endl;

	// Use the state stores in the return value of for_each!
	cout << "'" << mResult.m_nCount << "' elements were displayed!" << endl;

	return 0;
}