qtrap.c

可以用于科学计算的库

#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=0.0;

	for (j=1;j<=JMAX;j++) {
		s=trapzd(func,a,b,j);
		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;
}
#undef EPS
#undef JMAX