qtrap.c

来自「numerical recipes in C source codes」· C语言 代码 · 共 25 行

#include <math.h>
#define EPS 1.0e-5
#define JMAX 20

float qtrap(float (*func)(float), float a, float b)
{
	float trapzd(float (*func)(float), float a, float b, int n);
	void nrerror(char error_text[]);
	int j;
	float s,olds;

	olds = -1.0e30;
	for (j=1;j<=JMAX;j++) {
		s=trapzd(func,a,b,j);
		if (fabs(s-olds) < EPS*fabs(olds)) return s;
		if (s == 0.0 && olds == 0.0 && j > 6) return s;
		olds=s;
	}
	nrerror("Too many steps in routine qtrap");
	return 0.0;
}
#undef EPS
#undef JMAX
/* (C) Copr. 1986-92 Numerical Recipes Software "U,6VV'. */