什么是“双”在ceil（双）吗？ [英] What does the "double" do in ceil(double)?

问题描述

我有一个数字（让我们说，34），我想找到它的十的下一个倍数。我可以这样做：

I have a number (let's say, 34), and I want to find its next multiple of ten. I can do this by:

1. 将数字除以10




3. 乘以10。

经过一番研究，在Objective C中的代码：

After a bit of research, I discovered that this is the code for that in Objective C:

int number = 34;
int roundedNumber = ceil((double)number/10)*10;

我的问题是：（double） for，为什么删除（double）导致它舍入而不是向上？

My question is: what is the (double) for, and why does removing (double) cause it to round down instead of up?

从googling，将浮动格式更改为双精度，但老实说，这对我来说太复杂了。任何人都可以提供一个简单的解释，它在做什么？

I understand from googling that changes the float format to "double precision" but, to be honest, this is way too complicated for me. Can anyone provide a simple explanation of what it is doing?

推荐答案

如果您没有投放，则会发生以下情况（如果数字为34）。

If you don't have the cast the following happens (if number is 34).

1. 使用整数运算，数字/ 10是数字/ 10向下舍入，即3。


2. ceil（3） / li>
   
3. 3 * 10 = 30

如果您有演员， p>

If you have the cast, the following happens:

1. （double）number = 34.0


2. 34.0 / 10 = 3.4


3. ceil（3.4）= 4.0


4. 4.0 * 10 = 40

1. (double)number = 34.0
2. 34.0 / 10 = 3.4
3. ceil(3.4) = 4.0
4. 4.0*10 = 40

要实现的是整数除法总是向0舍入。

The important thing to realise is Integer division always rounds towards 0.

这篇关于什么是“双”在ceil（双）吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！