j0

接口定义

C interface：

float j0f(float x);

double j0(double x);

参数

返回值

• 返回以0阶第一类贝塞尔函数值y，y ∈ (-1, +1]，该函数为偶函数。
• 输入x为±0，返回1。
• 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("j0(0.0) = %.15f\n", j0(x1));
    printf("j0(-0.0) = %.15f\n", j0(x2));
    printf("j0(1.5) = %.15f\n", j0(x3));
    printf("j0(-2.5) = %.15f\n", j0(x4));
    printf("j0(INFINITY) = %.15f\n", j0(a));
    printf("j0(-INFINITY) = %.15f\n", j0(b));
    printf("j0(NAN) = %.15f\n", j0(c));

    /* 
     * j0(0.0) = 1.000000000000000
     * j0(-0.0) = 1.000000000000000
     * j0(1.5) = 0.511827671735918
     * j0(-2.5) = -0.048383776468198
     * j0(INFINITY) = 0.000000000000000
     * j0(-INFINITY) = 0.000000000000000
     * j0(NAN) = nan
     * 
     * */