eulsum.cpp

van wijngaarden方法求取解析函数在某点x0得领域内得展开成级数

#include <math.h>

void eulsum(float *sum, float term, int jterm, float wksp[])
{
	int j;
	static int nterm;
	float tmp, dum;

	if(jterm==1){
		nterm = 1;
		*sum = 0.5*(wksp[1]=term);
	}
	else{
		tmp = wksp[1];
		wksp[1] = term;
		for(j=1; j<nterm-1; j++){
			dum = wksp[j+1];
			wksp[j+1] = 0.5 * (wksp[j]+tmp);
			tmp  = dum;
		}
	}
	wksp[nterm+1] = 0.5 * (wksp[nterm]+tmp);
	if(fabs(wksp[nterm+1])<=fabs(wksp[nterm])){
		*sum += (0.5*wksp[++nterm]);
	}
	else{
		*sum += wksp[nterm+1];
	}
}