问题描述
我有一个名为 x 的 double 变量.在代码中，x 被分配了一个 0.1 的值，我在比较 x 和 0.1<的if"语句中检查它/代码>
I've a double variable called x.
In the code, x gets assigned a value of 0.1 and I check it in an 'if' statement comparing x and 0.1
if (x==0.1)
{
----
}
可惜没有进入if语句
我应该使用
Double还是double?
这背后的原因是什么?您能为此提出解决方案吗?
What's the reason behind this? Can you suggest a solution for this?
推荐答案
由于计算机如何存储浮点值，这是一个标准问题.在此处搜索浮点问题"，您会发现大量信息.
It's a standard problem due to how the computer stores floating point values. Search here for "floating point problem" and you'll find tons of information.
简而言之——float/double 不能精确地存储 0.1.总会有一点偏差.
In short – a float/double can't store 0.1 precisely. It will always be a little off.
您可以尝试使用 decimal 类型，它以十进制表示法存储数字.因此 0.1 将可以精确表示.
You can try using the decimal type which stores numbers in decimal notation. Thus 0.1 will be representable precisely.
你想知道原因:
Float/double 存储为二进制分数，而不是十进制分数.举例说明:
Float/double are stored as binary fractions, not decimal fractions. To illustrate:
12.34 十进制表示法(我们使用的)是什么意思
12.34 in decimal notation (what we use) means
1 * 101 + 2 * 100 + 3 * 10-1 + 4 * 10-2计算机以相同的方式存储浮点数，不同之处在于它使用基数2:10.01表示
The computer stores floating point numbers in the same way, except it uses base 2: 10.01 means
1 * 21 + 0 * 20 + 0 * 2-1 + 1 * 2-2现在，您可能知道有些数字无法用我们的十进制表示法完全表示.例如，十进制的1/3是0.3333333….同样的事情发生在二进制符号中，除了不能精确表示的数字是不同的.其中有数字1/10.以二进制表示，即 0.000110011001100….
Now, you probably know that there are some numbers that cannot be represented fully with our decimal notation. For example, 1/3 in decimal notation is 0.3333333…. The same thing happens in binary notation, except that the numbers that cannot be represented precisely are different. Among them is the number 1/10. In binary notation that is 0.000110011001100….
由于二进制不能精确存储，所以采用四舍五入的方式存储.因此你的问题.
Since the binary notation cannot store it precisely, it is stored in a rounded-off way. Hence your problem.
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