qgaus.c

来自「c数值算法的源码」· C语言 代码 · 共 20 行

float qgaus(func,a,b)
float (*func)(),a,b;
{
	int j;
	float xr,xm,dx,s;
	static float x[]={0.0,0.1488743389,0.4333953941,
		0.6794095682,0.8650633666,0.9739065285};
	static float w[]={0.0,0.2955242247,0.2692667193,
		0.2190863625,0.1494513491,0.0666713443};

	xm=0.5*(b+a);
	xr=0.5*(b-a);
	s=0;
	for (j=1;j<=5;j++) {
		dx=xr*x[j];
		s += w[j]*((*func)(xm+dx)+(*func)(xm-dx));
	}
	return s *= xr;
}