“双”是什么意思？在天花板上做（双）？
我有一个数字（假设是 34），我想找到它的下一个 10 的倍数。我可以通过以下方法做到这一点：
- 将数字除以 10
- 将其四舍五入为整数
- 乘以 10。
经过一番研究，我发现这是 Objective C 中的代码：
int number = 34;
int roundedNumber = ceil((double)number/10)*10;
我的问题是： (double) for，为什么删除 (double) 会导致它向下舍入而不是向上舍入？
我从谷歌搜索中了解到，将浮点格式更改为“双精度”，但说实话，这对我来说太复杂了。谁能简单解释一下它在做什么？
I have a number (let's say, 34), and I want to find its next multiple of ten. I can do this by:
- Dividing the number by 10
- Rounding it up to a whole number
- Multiplying by 10.
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;
My question is: what is the (double) for, and why does removing (double) cause it to round down instead of up?
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?
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如果您没有演员表，则会发生以下情况（如果数字为 34）。
如果进行强制转换，会发生以下情况：
需要认识到的重要一点是整数除法总是向 0 舍入。
If you don't have the cast the following happens (if number is 34).
If you have the cast, the following happens:
The important thing to realise is Integer division always rounds towards 0.
它将
number转换为double，以便执行浮点除法而不是整数除法。比较1/2与1.0/2。It casts
numberas adoubleso that float division is performed instead of integer division. Compare1/2versus1.0/2.