更改double值的格式并返回double的结果 [英] Change format of double value and return result as double

问题描述

你好，

我正在寻找一种方法来改变c语言中双值的格式，就像c＃中的以下命令一样：

Hi there,
I'm looking for a way to change format of my double value in c language like how the following command do in c#:

Math.Round(MyDoubleValue, 1);

所以它是圆形的，也可以截断到一个数字后浮点数。

但是我在我的搜索中找到的唯一的东西就像下面这样：

So it is rounded and also truncated to just one digit as float after dot.
But the only thing that i could find in my lots of searches was something like below :

sprintf("%.1f", MyDoubleValue);

它打印的确切是我想要的，但问题是我不想打印结果而且我想将它设置为另一个双变量。

有什么办法吗？

It prints exactly what i want, however the problem is that i do not want to print the result but also i want to set it to another double variable.
Is there any way?

推荐答案

check 舍入数字为C中的2个小数位数 [ ^ ]

check Rounding Number to 2 Decimal Places in C[^]

#include <math.h>

float val = 37.777779;

float rounded_down = floorf(val * 10) / 10;   /* Result: 37.7 */
float nearest = roundf(val * 10) / 10;  /* Result: 37.8 */
float rounded_up = ceilf(val * 10) / 10;      /* Result: 37.8 */</math.h>

标准C没有舍入函数：它确实有底线：

Standard C doesn't have a rounding function: it does have floor however:

float f = 12.3456;
float r = floor((f * 10.0) + 0.5) / 10.0;

应该这样做。

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