qtrap.cpp

来自「Numerical recipes in C++」· C++ 代码 · 共 22 行

#include <cmath>
#include "nr.h"
using namespace std;

DP NR::qtrap(DP func(const DP), const DP a, const DP b)
{
	const int JMAX=20;
	const DP EPS=1.0e-10;
	int j;
	DP s,olds=0.0;

	for (j=0;j<JMAX;j++) {
		s=trapzd(func,a,b,j+1);
		if (j > 5)
			if (fabs(s-olds) < EPS*fabs(olds) ||
				(s == 0.0 && olds == 0.0)) return s;
		olds=s;
	}
	nrerror("Too many steps in routine qtrap");
	return 0.0;
}