trapzint.cpp

这是一个VC环境下用C++写的变步长梯形求积分算法

#include "Trapzint.h"
double Trapz::operator ()(double a,double b,double eps)const
{
	int done(0);
	int n;
	double h,Tn,T2n;
	n=1;
	h=b-a;
	Tn=h*(f(a)+f(b))/2.0;
	while(!done)
	{
		double temp(0.0);
		for(int k=0;k<n;k++)
		{
			double x=a+(k+0.5)*h;
			temp+=f(x);
		}
		T2n=(Tn+h*temp)/2.0;
		if(fabs(T2n-Tn)<eps)done=1;
		else
		{
			Tn=T2n;
			n*=2;
			h/=2;
		}
	}
	return T2n;
}