y1

接口定义

C interface：

float y1f(float x);

double y1(double x);

参数

返回值

• 返回以1阶第二类贝塞尔函数值y，y ∈ (-∞, +1)。
• 输入x为±0，返回-∞。
• 输入x<0，返回nan。
• 输入x为+∞，返回0。
• 输入x为nan，返回nan。

依赖

C: "km.h"

示例

C interface：

    double x1 = 0.0, x2 = -0.0, x3 = 1.5, x4 = -2.5;
    // special handing
    double a = INFINITY, b = -INFINITY, c = NAN;
    // print result
    printf("y1(0.0) = %.15f\n", y1(x1));
    printf("y1(-0.0) = %.15f\n", y1(x2));
    printf("y1(1.5) = %.15f\n", y1(x3));
    printf("y1(-2.5) = %.15f\n", y1(x4));
    printf("y1(INFINITY) = %.15f\n", y1(a));
    printf("y1(-INFINITY) = %.15f\n", y1(b));
    printf("y1(NAN) = %.15f\n", y1(c));

    /* 
     * y1(0.0) = -inf
     * y1(-0.0) = -inf
     * y1(1.5) = -0.412308626973911
     * y1(-2.5) = nan
     * y1(INFINITY) = 0.000000000000000
     * y1(-INFINITY) = nan
     * y1(NAN) = nan
     * 
     * */