std::llrint

Defined in header <cmath>	?	?
float rint( float arg );	(1)	(since C++11)
double rint( double arg );	(2)	(since C++11)
long double rint( long double arg );	(3)	(since C++11)
double rint( Integral arg );	(4)	(since C++11)
long lrint( float arg );	(5)	(since C++11)
long lrint( double arg );	(6)	(since C++11)
long lrint( long double arg );	(7)	(since C++11)
long lrint( Integral arg );	(8)	(since C++11)
long long llrint( float arg );	(9)	(since C++11)
long long llrint( double arg );	(10)	(since C++11)
long long llrint( long double arg );	(11)	(since C++11)
long long llrint( Integral arg );	(12)	(since C++11)

1-3%29圈浮点参数arg为浮点格式%29的整数值%28，使用电流舍入模式...

5-7，9-11%29圈浮点参数arg值的整数值，则使用电流舍入模式...

4，8，12%29一组过载或接受任意参数的函数模板积分型。等于%282，6，10%29，分别为%28double29%。

参数

arg	-	floating point value

返回值

如果没有发生错误，则最近的整数值为arg，根据电流舍入模式，被归还。

错误处理

错误按数学[医]错误处理...

如果...的结果...std::lrint或std::llrint在返回类型可表示的范围之外，可能会发生域错误或范围错误。

如果实现支持ieee浮点算术%28iec 60559%29，则对std::rint职能：

如果arg是±∞，它被返回，未经修改

如果arg是±0，它被返回，未经修改

如果arg是南，南回来了

为std::lrint和std::llrint职能：

如果arg是±∞，FE_INVALID引发，并返回实现定义的值。

如果舍入的结果超出了返回类型的范围，FE_INVALID引发，并返回实现定义的值。

如果arg是南FE_INVALID引发，并返回实现定义的值。

注记

POSIX指定所有案件std::lrint或std::llrint提高FE_INEXACT是域错误。

如数学[医]错误处理，，，FE_INEXACT可能为%28，但%27T是否需要在非ieee浮点平台上由std::rint当舍入一个非整数的有限值时。

唯一的区别是std::rint和std::nearbyint那是std::nearbyint不养FE_INEXACT...

最大的可表示浮点值是所有标准浮点格式的精确整数，因此std::rint永远不要自己溢出，但是结果可能会溢出任何整数类型%28，包括std::intmax_t%29，存储在整数变量中。

如果当前舍入模式是..。

FE_DOWNWARD，然后std::rint等于std::floor...

FE_UPWARD，然后std::rint等于std::ceil...

FE_TOWARDZERO，然后std::rint等于std::trunc

FE_TONEAREST，然后std::rint不同于std::round在这中间的情况是四舍五入，而不是远离零。

例

二次

#include <iostream>
#include <cmath>
#include <cfenv>
#include <climits>
 
int main()
{
#pragma STDC FENV_ACCESS ON
    std::fesetround(FE_TONEAREST);
    std::cout << "rounding to nearest (halfway cases to even):\n"
              << "rint(+2.3) = " << std::rint(2.3)
              << "  rint(+2.5) = " << std::rint(2.5)
              << "  rint(+3.5) = " << std::rint(3.5) << '\n'
              << "rint(-2.3) = " << std::rint(-2.3)
              << "  rint(-2.5) = " << std::rint(-2.5)
              << "  rint(-3.5) = " << std::rint(-3.5) << '\n';
 
    std::fesetround(FE_DOWNWARD);
    std::cout << "rounding down:\n" 
              << "rint(+2.3) = " << std::rint(2.3)
              << "  rint(+2.5) = " << std::rint(2.5)
              << "  rint(+3.5) = " << std::rint(3.5) << '\n'
              << "rint(-2.3) = " << std::rint(-2.3)
              << "  rint(-2.5) = " << std::rint(-2.5)
              << "  rint(-3.5) = " << std::rint(-3.5) << '\n'
              << "rounding down with lrint\n" 
              << "lrint(+2.3) = " << std::lrint(2.3)
              << "  lrint(+2.5) = " << std::lrint(2.5)
              << "  lrint(+3.5) = " << std::lrint(3.5) << '\n'
              << "lrint(-2.3) = " << std::lrint(-2.3)
              << "  lrint(-2.5) = " << std::lrint(-2.5)
              << "  lrint(-3.5) = " << std::lrint(-3.5) << '\n';
 
    std::cout << "lrint(-0.0) = " << std::lrint(-0.0)  << '\n'
              << "lrint(-Inf) = " << std::lrint(-INFINITY) << '\n';
 
    // error handling
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "std::rint(0.1) = " << std::rint(.1) << '\n';
    if(std::fetestexcept(FE_INEXACT))
              std::cout << "    FE_INEXACT was raised\n";
 
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout << "std::lrint(LONG_MIN-2048.0) = "
              << std::lrint(LONG_MIN-2048.0) << '\n';
    if(std::fetestexcept(FE_INVALID))
              std::cout << "    FE_INVALID was raised\n";
}

二次

可能的产出：

二次

rounding to nearest (halfway cases to even): 
rint(+2.3) = 2  rint(+2.5) = 2  rint(+3.5) = 4
rint(-2.3) = -2  rint(-2.5) = -2  rint(-3.5) = -4
rounding down:
rint(+2.3) = 2  rint(+2.5) = 2  rint(+3.5) = 3
rint(-2.3) = -3  rint(-2.5) = -3  rint(-3.5) = -4
rounding down with lrint
lrint(+2.3) = 2  lrint(+2.5) = 2  lrint(+3.5) = 3
lrint(-2.3) = -3  lrint(-2.5) = -3  lrint(-3.5) = -4
lrint(-0.0) = 0
lrint(-Inf) = -9223372036854775808
std::rint(0.1) = 0
    FE_INEXACT was raised
std::lrint(LONG_MIN-2048.0) = -9223372036854775808
    FE_INVALID was raised

二次

另见

trunc (C++11)	nearest integer not greater in magnitude than the given value (function)
nearbyint (C++11)	nearest integer using current rounding mode (function)
fegetroundfesetround (C++11)(C++11)	gets or sets rounding direction (function)

c Rint文件

 ? cppreference.com

在CreativeCommonsAttribution下授权-ShareAlike未移植许可v3.0。

http：//en.cppreference.com/w/cpp/NUMERIC/MATH/Rint

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最后更新于：2017-12-18