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std::trunc

STD：：trunc

Defined in header ​​
float trunc( float arg (1)(since C++11)
double trunc( double arg (2)(since C++11)
long double trunc( long double arg (3)(since C++11)
double trunc( Integral arg (4)(since C++11)

1-3%29计算最接近的整数，其大小不大于arg...

4%29一组过载或接受任意参数的函数模板积分型等于2%29%28double29%。

参数

arg-floating point value

返回值

如果没有发生错误，则最近的整数值在大小上不大于arg%28，换言之，arg四舍五入至零%29，返回。

返回值

二次

二次

论辩

错误处理

错误按数学[医]错误处理...

如果实现支持ieee浮点算法%28IEC 60559%29，

  • 电流舍入方式没有效果。

  • 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

  • 如果阿格是南，南就会被归还。

注记

FE_INEXACT可能为%28，但在截断非整数有限值时，%27T是否需要提高%29。

最大的可表示浮点值是所有标准浮点格式的精确整数，因此此函数本身不会溢出，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。

大隐式转换从浮点类型到整型，也是圆圈到零，但仅限于目标类型可以表示的值。

例

二次

#include <cmath>
#include <iostream>
int main()
{
    std::cout << std::fixed
              << "trunc(+2.7) = " << std::trunc(+2.7) << '\n'
              << "trunc(-2.9) = " << std::trunc(-2.9) << '\n'
              << "trunc(-0.0) = " << std::trunc(-0.0) << '\n'
              << "trunc(-Inf) = " << std::trunc(-INFINITY) << '\n';
}

二次

可能的产出：

二次

trunc(+2.7) = 2.000000
trunc(-2.9) = -2.000000
trunc(-0.0) = -0.000000
trunc(-Inf) = -inf

二次

另见

floornearest integer not greater than the given value (function)
ceilnearest integer not less than the given value (function)
roundlroundllround (C++11)(C++11)(C++11)nearest integer, rounding away from zero in halfway cases (function)

C.trunc的文档

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http：//en.cppreference.com/w/cpp/数值/数学/trunc

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