std::fegetround
Defined in header <cfenv> | ? | ? |
|---|---|---|
int fesetround( int round ) | (1) | (since C++11) |
int fegetround() | (2) | (since C++11) |
管理浮点舍入方向。
1%29尝试建立与参数相等的浮点舍入方向。round，这将是浮点四舍五入宏...
2%29返回浮点舍入宏它对应于当前的舍入方向。
参数
round | - | rounding direction, one of floating point rounding macros |
|---|
返回值
1%29?0?在成功的时候，不是零，否则。
2%29浮点舍入宏描述当前的四舍五入方向或一个负值，如果无法确定该方向。
注记
当前的舍入模式，反映了最近的fesetround，也可以用FLT_ROUNDS...
见浮点四舍五入宏四舍五入的效果。
例
二次
#include <cmath>
#include <cfenv>
#include <iostream>
int main()
{
#pragma STDC FENV_ACCESS ON
std::fesetround(FE_DOWNWARD);
std::cout << "rounding using FE_DOWNWARD: \n" << std::fixed
<< " 12.0 -> " << std::nearbyint(12.0) << '\n'
<< " 12.1 -> " << std::nearbyint(12.1) << '\n'
<< "-12.1 -> " << std::nearbyint(-12.1) << '\n'
<< " 12.5 -> " << std::nearbyint(12.5) << '\n'
<< " 12.9 -> " << std::nearbyint(12.9) << '\n'
<< "-12.9 -> " << std::nearbyint(-12.9) << '\n'
<< " 13.0 -> " << std::nearbyint(13.0) << '\n';
std::fesetround(FE_TONEAREST);
std::cout << "rounding using FE_TONEAREST: \n"
<< " 12.0 -> " << std::nearbyint(12.0) << '\n'
<< " 12.1 -> " << std::nearbyint(12.1) << '\n'
<< "-12.1 -> " << std::nearbyint(-12.1) << '\n'
<< " 12.5 -> " << std::nearbyint(12.5) << '\n'
<< " 12.9 -> " << std::nearbyint(12.9) << '\n'
<< "-12.9 -> " << std::nearbyint(-12.9) << '\n'
<< " 13.0 -> " << std::nearbyint(13.0) << '\n';
}二次
产出：
二次
rounding using FE_DOWNWARD:
12.0 -> 12.000000
12.1 -> 12.000000
-12.1 -> -13.000000
12.5 -> 12.000000
12.9 -> 12.000000
-12.9 -> -13.000000
13.0 -> 13.000000
rounding using FE_TONEAREST:
12.0 -> 12.000000
12.1 -> 12.000000
-12.1 -> -12.000000
12.5 -> 12.000000
12.9 -> 13.000000
-12.9 -> -13.000000
13.0 -> 13.000000二次
另见
nearbyint (C++11) | nearest integer using current rounding mode (function) |
|---|---|
rintlrintllrint (C++11)(C++11)(C++11) | nearest integer using current rounding mode with exception if the result differs (function) |
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