bessy.cpp

零阶、一阶和任意整数阶的第一二类贝赛尔函数算法

double bessy(int n, double x)
{
	double tox,by,bym,byp,temp;
	int j;
    if (n < 2)
	{
        cout<<"bad argument n in bessy";
        _c_exit();
	}
    tox = 2.0 / x;
    by = bessy1(x);
    bym = bessy0(x);
    for( j = 1;j<=n-1;j++)
	{
        byp = j * tox * by - bym;
        bym = by;
        by = byp;
    }
    temp = by;
	return temp;
}