powr8i4

接口定义

C interface：

double powr8i4(double x, int y);

参数

返回值

• x任意，y为0，返回1.0。
• x为INF，y为正整数，返回INF。
• x为INF，y为负整数，返回0.0。
• x为-INF，y为正奇数，返回-INF。
• x为-INF，y为正偶数，返回INF。
• x为-INF，y为负奇数，返回-0.0。
• x为-INF，y为负偶数，返回0.0。
• x为NAN，y任意，返回NAN。
• x为-0.0，y为负整数，返回-INF。
• x为0.0，y为负整数，返回INF。
• x为大的有限数，y为大的整数，返回+/-INF。

依赖

C: "km.h"

示例

C interface:

   // typical usage 
    double  x1 = 1.0, x2 = 2.0, x3 = 3.0, x4 = 4.0;
    int  y1 = 4, y2 = -4, y3 = -3, y4 = 3;
    // special handing 
    double a = INFINITY, b = -INFINITY, c = NAN, d = 0.0; 
    // print result 
    printf("pow(1.0, 4) = %.15f\n", pow(x1, y1));
    printf("pow(2.0, -4) = %.15f\n", pow(x2, y2));
    printf("pow(3.0, -3) = %.15f\n", pow(x3, y3));
    printf("pow(4.0, 3) = %.15f\n", pow(x4, y4));
    printf("pow(INFINITY, 4) = %+.15f\n", pow(a, y1));
    printf("pow(INFINITY, -4) = %+.15f\n", pow(a, y2));
    printf("pow(-INFINITY, -3) = %+.15f\n", pow(b, y3));
    printf("pow(NAN, 3) = %+.15f\n", pow(c, y4));
    printf("pow(0.0, -3) = %+.15f\n", pow(d, y3));
    printf("pow(-0.0, -3) = %+.15f\n", pow(e, y3));
    /* 
     *  pow(1.0, 4) = 1.000000000000000
     *  pow(2.0, -4) = 0.062500000000000
     *  pow(3.0, -3) = 0.037037037037037
     *  pow(4.0, 3) = 64.000000000000000
     *  pow(INFINITY, 4) = inf
     *  pow(INFINITY, -4) = 0.000000000000000
     *  pow(-INFINITY, -3) = -0.000000000000000
     *  pow(NAN, 3) = nan
     *  pow(0.0, -3) = inf
     *  pow(-0.0, -3) = -inf
     * 
     * */