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文字

在头文件<math.h>中定义



float       tgammaf( float arg );

(1)

(since C99)

double      tgamma( double arg );

(2)

(since C99)

long double tgammal( long double arg );

(3)

(since C99)

Defined in header <tgmath.h>



#define tgamma( arg )

(4)

(since C99)

1-3)计算arg的伽马函数。

4)类型通用宏:如果arg的类型为long double,则调用tgammal。 否则,如果arg具有整数类型或类型double,则调用tgamma。 否则,调用tgammaf。

参数

ARG

-

浮点值

返回值

如果没有发生错误,则arg的伽马函数的值即∫∞

0_t_arg-1

返回e -td t

如果发生域错误,则返回实现定义的值(NaN,如果支持)。

如果发生极点错误,则返回±HUGE_VAL,±HUGE_VALF或±HUGE_VALL。

如果发生由溢出引起的范围错误,则返回±HUGE_VAL,±HUGE_VALF或±HUGE_VALL。

如果发生由于下溢导致的范围错误,则返回正确的值(舍入后)。

错误处理

按照math_errhandling中的指定报告错误。

如果arg是零或者是小于零的整数,则可能发生极点错误或域错误。

如果实现支持IEEE浮点运算(IEC 60559),

如果参数为±0,则返回±∞并引发FE_DIVBYZERO

如果参数是一个负整数,则返回NaN并引发FE_INVALID

如果参数是-∞,则返回NaN并引发FE_INVALID

如果参数是+∞,则返回+∞。

如果参数是NaN,则返回NaN

注意

如果arg是自然数,则tgamma(arg)是arg-1的阶乘。 如果参数是一个足够小的整数,许多实现计算确切的整数域因子。

对于兼容IEEE的类型,如果0 <x <1 / DBL_MAX或者x> 171.7,则发生溢出。

如果参数为零,则POSIX要求出现极点错误,但当参数为负整数时会出现域错误。它还规定将来,域误差可能被负整数参数的极点误差所替代(在这种情况下,这些情况下的返回值将从NaN变为±∞)。

在各种实现中有一个名为gamma的非标准函数,但其定义不一致。 例如,gamma的glibc和4.2BSD版本执行lgamma,但4.4BSD版本的gamma执行tgamma。

#include <stdio.h>#include <math.h>#include <float.h>#include <errno.h>#include <fenv.h>#pragma STDC FENV_ACCESS ON
int main(void){    printf("tgamma(10) = %f, 9!=%f\n", tgamma(10), 2*3*4*5*6*7*8*9.0);    printf("tgamma(0.5) = %f, sqrt(pi) = %f\n", sqrt(acos(-1)), tgamma(0.5));    // special values    printf("tgamma(+Inf) = %f\n", tgamma(INFINITY));    //error handling
    errno = 0; feclearexcept(FE_ALL_EXCEPT);    printf("tgamma(-1) = %f\n", tgamma(-1));    if(errno == ERANGE) perror("    errno == ERANGE");    else if(errno == EDOM)   perror("    errno == EDOM");    if(fetestexcept(FE_DIVBYZERO)) puts("    FE_DIVBYZERO raised");    else if(fetestexcept(FE_INVALID)) puts("    FE_INVALID raised");}

可能的输出:

tgamma(10) = 362880.000000, 9!=362880.000000tgamma(0.5) = 1.772454, sqrt(pi) = 1.772454tgamma(+Inf) = inftgamma(-1) = nan
    errno == EDOM: Numerical argument out of domain
    FE_INVALID raised

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.12.8.4 tgamma函数(p:250)

    • 7.25类型通用数学<tgmath.h>(p:373-375)

    • F.10.5.4 tgamma函数(p:525)

  • C99标准(ISO / IEC 9899:1999):

    • 7.12.8.4 tgamma函数(p:231)

    • 7.22类型通用数学<tgmath.h>(p:335-337)

    • F.9.5.4 tgamma函数(p:462)

扩展内容

lgammalgammaflgammal(C99)(C99)(C99)

计算伽玛函数(函数)的自然(基-e)对数,

| tgamma的C ++文档 |

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