计算x的伽马值绝对值的自然对数，返回伽马值的符号，输入参数为实数。

接口定义

C interface：

float lgammaf_r(float x);

double lgamma_r(double x);

参数

参数名	类型	描述	输入/输出
x	在lgammaf_r中，x是单精度浮点类型。在lgamma_r中，x是双精度浮点类型。	表示输入数据的浮点值。	输入

返回值

返回入参x的伽马值绝对值的自然对数、伽马值的符号。
输入nan，返回nan，符号为1。
输入+∞，返回+∞，符号为1。
输入-∞，返回+∞，符号为1。
输入+0，返回+∞，符号为1。
输入-0，返回+∞，符号为-1。

依赖

C: "km.h"

示例

C interface：

    // print result
    int sign=0;
    double res=0.0;
    res=lgamma_r(0.0, &sign);
    printf("lgamma_r(0.0, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-0.0, &sign);
    printf("lgamma_r(-0.0, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(0.25, &sign);
    printf("lgamma_r(0.25, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-0.25, &sign);
    printf("lgamma_r(-0.25, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(0.5, &sign);
    printf("lgamma_r(0.5, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-0.5, &sign);
    printf("lgamma_r(-0.5, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(1.0, &sign);
    printf("lgamma_r(1.0, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-1.0, &sign);
    printf("lgamma_r(-1.0, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(2.0, &sign);
    printf("lgamma_r(2.0, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-2.0, &sign);
    printf("lgamma_r(-2.0, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(INFINITY, &sign);
    printf("lgamma_r(INFINITY, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-INFINITY, &sign);
    printf("lgamma_r(-INFINITY, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(NAN, &sign);
    printf("lgamma_r(NAN, &sign) = %.15f, sign = %d\n", res, sign);
    res=lgamma_r(-NAN, &sign);
    printf("lgamma_r(-NAN, &sign) = %.15f, sign = %d\n", res, sign);
    /* 
     * lgamma_r(0.0, &sign) = inf, sign = 1
     * lgamma_r(-0.0, &sign) = inf, sign = -1
     * lgamma_r(0.25, &sign) = 1.288022524698077, sign = 1
     * lgamma_r(-0.25, &sign) = 1.589575312551186, sign = -1
     * lgamma_r(0.5, &sign) = 0.572364942924700, sign = 1
     * lgamma_r(-0.5, &sign) = 1.265512123484645, sign = -1
     * lgamma_r(1.0, &sign) = 0.000000000000000, sign = 1
     * lgamma_r(-1.0, &sign) = inf, sign = 1
     * lgamma_r(2.0, &sign) = 0.000000000000000, sign = 1
     * lgamma_r(-2.0, &sign) = inf, sign = 1
     * lgamma_r(INFINITY, &sign) = inf, sign = 1
     * lgamma_r(-INFINITY, &sign) = inf, sign = 1
     * lgamma_r(NAN, &sign) = nan, sign = 1
     * lgamma_r(-NAN, &sign) = -nan, sign = 1
     * 
     * */