simpson.cpp

simpson算法

#include<iostream>
#include<math.h>
using namespace std;
double funcA(double x)
{
	return x*cos(x*x);
}
double funcB(double x)
{
	return x*sin(x*x);
}
double funcC(double x)
{
	return x*x*cos(x);
}
double funcD(double x)
{
	return x*x*sin(x);
}
double simpson(double a,double b,int n,double(*f)(double))
{
	double h=(b-a)/n;
	double xi0=(*f)(a)+(*f)(b);
	double xi1=0;
	double xi2=0;
	for(int i=1;i<n;i++)
	{
		double x=a+i*h;
		if(i%2==0)
		{
			xi2=xi2+(*f)(x);
		}
		else
		{
			xi1=xi1+(*f)(x);
		}

	}
	double xi=h*(xi0+2*xi2+4*xi1)/3;
	return xi;
}
int main()
{
	double a,b;
	int n=4;
	//cin>>a;
	//cin>>b;
	//cin>>n;
	while(n<30)
	{
		cout<<"The result of integral is:"<<simpson(0,3.141592653,n,funcD)<<endl;
		n+=2;
	}
	return 0;
}