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在头文件<stdlib.h>中定义



float       remainderf( float x, float y );

(1)

(since C99)

double      remainder( double x, double y );

(2)

(since C99)

long double remainderl( long double x, long double y );

(3)

(since C99)

Defined in header <tgmath.h>



#define remainder( x, y )

(4)

(since C99)

1-3)计算浮点除法运算的IEEE余数x/y

4)类型 - 通用宏:如果任何参数具有类型long doubleremainderl则被调用。否则,如果任何参数具有整数类型或具有类型doubleremainder则被调用。否则,remainderf被调用。

x/y由该函数计算的除法操作的IEEE浮点余数恰好是该值x - n*y,其中该值n是与精确值最接近的整数值x/y。当| nx / y |时 =½,该值n被选为偶数。

与之相反fmod(),返回的值不能保证具有相同的符号x

如果返回的值是0,它将具有与。相同的符号x

参数

x,y

-

浮点值

返回值

如果成功,则返回x/y如上定义的除法的IEEE浮点余数。

如果发生域错误,则返回实现定义的值(NaN,如果支持)。

如果由于下溢而发生范围错误,则返回正确的结果。

如果y为零,但域错误不会发生,则返回零。

错误处理

按照math_errhandling中的指定报告错误。

如果y为零,则可能会出现域错误。

如果实现支持IEEE浮点运算(IEC 60559),

  • 当前的舍入模式不起作用。

  • FE_INEXACT 永远不会升起,结果总是确切的。

  • 如果x是±∞并且y不是NaN,则返回并FE_INVALID提升NaN

  • 如果y是±0并且x不是NaN,则返回并FE_INVALID提升NaN

  • 如果任一参数是NaN,则返回NaN

笔记

如果x是无限的或者y是零,POSIX要求发生域错误。

fmod,但remainder对于将浮点类型静默包装为无符号整数类型非常有用:(0.0 <= (y = fmod(rint(x), 65536.0)) ? y : 65536.0 + y)处于范围内[-0.0 .. 65535.0],该范围与范围相对应unsigned short,但remainder(rint(x), 65536.0位于范围[-32767.0, +32768.0]之外的范围内signed short

#include <stdio.h>#include <math.h>#include <fenv.h>
 #pragma STDC FENV_ACCESS ON
int main(void){    printf("remainder(+5.1, +3.0) = %.1f\n", remainder(5.1,3));    printf("remainder(-5.1, +3.0) = %.1f\n", remainder(-5.1,3));    printf("remainder(+5.1, -3.0) = %.1f\n", remainder(5.1,-3));    printf("remainder(-5.1, -3.0) = %.1f\n", remainder(-5.1,-3)); 
    // special values    printf("remainder(-0.0, 1.0) = %.1f\n", remainder(-0.0, 1));    printf("remainder(+5.1, Inf) = %.1f\n", remainder(5.1, INFINITY)); 
    // error handling    feclearexcept(FE_ALL_EXCEPT);    printf("remainder(+5.1, 0) = %.1f\n", remainder(5.1, 0));    if(fetestexcept(FE_INVALID)) puts("    FE_INVALID raised");}

输出:

remainder(+5.1, +3.0) = -0.9remainder(-5.1, +3.0) = 0.9remainder(+5.1, -3.0) = -0.9remainder(-5.1, -3.0) = 0.9remainder(+0.0, 1.0) = 0.0remainder(-0.0, 1.0) = -0.0remainder(+5.1, Inf) = 5.1remainder(+5.1, 0) = -nan
    FE_INVALID raised

参考

  • C11标准(ISO / IEC 9899:2011):

    • 7.12.10.2其余职能(p:254-255)

    • 7.25类型通用数学<tgmath.h>(p:373-375)

    • F.10.7.2其余功能(p:529)

  • C99标准(ISO / IEC 9899:1999):

    • 7.12.10.2其余职能(p:235)

    • 7.22类型通用数学<tgmath.h>(p:335-337)

    • F.9.7.2其余功能(p:465)

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