使用std::accumulate计算和、积和平均值

class DPoint

{

public:

	DPoint(double _x,double _y, double _z)

		: x(_x),y(_y),z(_z){}



	double x;

	double y;

	double z;

};



class PointAverage: public binary_function<DPoint, DPoint, DPoint>

{

public:

	PointAverage():xSum(0),ySum(0),zSum(0),numPoints(0){}

	const DPoint operator()(const DPoint& avgSoFar, const DPoint& p)

	{

		++numPoints;

		xSum += p.x;

		ySum += p.y;

		zSum += p.z;

		return DPoint(xSum/numPoints,ySum/numPoints,zSum/numPoints);

	}



private:

	double xSum;

	double ySum;

	double zSum;

	size_t numPoints;

};



int main() 

{



	list<double> ld;

	ld.push_back(1.0);

	ld.push_back(2.0);

	ld.push_back(3.0);

	ld.push_back(4.0);

	double sum = accumulate(ld.begin(),ld.end(),0.0);

	cout<<sum<<endl;



	double product = accumulate(ld.begin(),ld.end(),1.0,multiplies<double>());

	cout<<product<<endl;



	vector<DPoint> pv;

	pv.push_back(DPoint(2,3,5));

	pv.push_back(DPoint(3,4,5));

	pv.push_back(DPoint(5,6,2));



	

	DPoint avg = accumulate(pv.begin(),pv.end(),DPoint(0,0,0),PointAverage());

	cout<<avg.x<<" "<<avg.y<<" "<<avg.z<<endl;



}