ex.cpp

来自「工程算法 这是一个很有用的工程数值算法集锦」· C++ 代码 · 共 32 行

double ex(double x)
{
	double r1,r2,r3,r4,r5,r6,t1,t2,t3,t4,s1,s2,s3,s4,temp,aaa,y,w;
    r1 = 0.00107857;
    r2 = -0.00976004;
    r3 = 0.05519968;
    r4 = -0.24991055;
    r5 = 0.99999193;
    r6 = -0.57721566;
    t1 = 8.5733287401;
    t2 = 18.059016973;
    t3 = 8.6347608925;
    t4 = 0.2677737343;
    s1 = 9.5733223454;
    s2 = 25.6329561486;
    s3 = 21.0996530827;
    s4 = 3.9584969228;
    if (x < 1.0)
	{
        aaa = (r1 * x + r2) * x + r3;
        temp = ((aaa * x + r4) * x + r5) * x + r6 - log(x);
	}
    else
	{
        y = (((x + t1) * x + t2) * x + t3) * x + t4;
        w = (((x + s1) * x + s2) * x + s3) * x + s4;
        temp = (y / w) / (exp(x) * x);
	}
	return temp;
}