blocks|key|1286556|text|如果你很好奇，这就是Double.IsNaN的样子：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1286557|public+static+bool+IsNaN(double+d)
{
++++return+(d+!=+d);
}|code-block|syntax|javascript|1286558|很时髦，是吧？|1286559|entityMap^0|A|C|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

If you are curious, this is what <code>Double.IsNaN</code> looks like:

<pre><code>public static bool IsNaN(double d)
{
 return (d != d);
}
</code></pre>

Funky, huh?

blocks|key|1286367|text|使用Double.IsNaN。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1286368|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.double.isnan.aspx^0|2|C|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Use <a href="http://msdn.microsoft.com/en-us/library/system.double.isnan.aspx" rel="noreferrer">Double.IsNaN</a>.

blocks|key|1501233|text|bool+isNaN+=+Double.IsNaN(yourNumber)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1501234|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>bool isNaN = Double.IsNaN(yourNumber)
</code></pre>

blocks|key|1286528|text|在这里使用Double.IsNan()测试等价性。原因是NaN不是一个数字。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1286529|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/system.double.isnan(VS.71).aspx^0|5|E|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

Use <a href="http://msdn.microsoft.com/en-us/library/system.double.isnan(VS.71).aspx" rel="noreferrer">Double.IsNan()</a> to test for equality here. The reason is that NaN is not a number.

blocks|key|1501272|text|这里有一个专门的函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1501273|double.IsNan(huh);|code-block|syntax|javascript|1501274|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

There's a specialized function for this:

<pre><code>double.IsNan(huh);
</code></pre>

blocks|key|1501333|text|使用"Double.IsNaN(+value+)“方法检查此条件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1501334|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Use the method "Double.IsNaN( value )" to check for this condition.

blocks|key|1286642|text|实际上，您已经找到了检查IEEE-754浮点数是否为NaN的方法:它是唯一的浮点值(或值范围，因为有几个NaN)，如果与其本身进行比较，它的计算结果为False，即：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1286643|bool+isNaN(double+v)+{
++++return+v+!=+v;
}|code-block|syntax|javascript|1286644|在幕后，Double.IsNaN方法实际上可能会做同样的事情。您仍然应该使用它，因为它的行为对于任何不了解FP标准的人来说都是相当令人惊讶的。|1286645|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/NaN^0|23|5|Q|3|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@$9|X|A|Y|1|Z]]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|11|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|12|8|@]|D|@]|E|$]]]|N|$O|$5|P|Q|R|E|$S|T]]]]

Actually, you already found the way to check if a IEEE-754 floating point number is <a href="http://en.wikipedia.org/wiki/NaN" rel="nofollow noreferrer">NaN</a>: it is the only floating point value (or range of values, because there are several NaNs) that evaluates to <code>False</code> if compared to itself, i.e. :

<pre><code>bool isNaN(double v) {
 return v != v;
}
</code></pre>

Under the hood, the Double.IsNaN method might actually do the same thing. You should still use it, because the behavior is quite surprising to anybody who does not know about the FP standard.

blocks|key|1501528|text|关于NaN，我们唯一知道的就是它“不是一个数字”。这并不意味着它有一个可以与其状态关联的值。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1501529|-∞%2B(+NaN+)=∞|1501530|0/0+=+NaN|1501531|(-∞%2B+(∞))+<>+(0/0)|1501532|下面是一些演示的C#|1501533|var+infinity+=+100d+/+0;
var+negInfinity+=+-100d+/+0;

var+notANumber+=+infinity+%2B+negInfinity;
Console.WriteLine("Negative+Infinity+plus+Infinity+is+NaN:+{0}",+double.IsNaN(notANumber));

var+notANumber2+=+0d+/+0d;
Console.WriteLine("Zero+divided+by+Zero+is+NaN:+{0}",+double.IsNaN(notANumber2));

Console.WriteLine("These+two+are+not+equal:+{0}",+notANumber+==+notANumber2);|code-block|syntax|javascript|1501534|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|U|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|V|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

The only thing that we know about NaN is that it's "Not a Number." That doesn't mean that it has a value that is associable with its state. For example:

&infin; + (-&infin;) = NaN

0/0 = NaN

(&infin; + (-&infin;)) &lt;> (0/0)

Here's some C# to demonstrate

<pre><code>var infinity = 100d / 0;
var negInfinity = -100d / 0;

var notANumber = infinity + negInfinity;
Console.WriteLine("Negative Infinity plus Infinity is NaN: {0}", double.IsNaN(notANumber));

var notANumber2 = 0d / 0d;
Console.WriteLine("Zero divided by Zero is NaN: {0}", double.IsNaN(notANumber2));

Console.WriteLine("These two are not equal: {0}", notANumber == notANumber2);
</code></pre>

blocks|key|1501580|text|使用Double.NaN+!=+Double.NaN的原因很简单：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1501581|你认为0/0会和Math.Sqrt(-3)一样吗？与Math.Sqrt(-7)相同|1501582|在我看来，C#中有一个bug，NaN没有覆盖Equals()。|1501583|Assert.IsTrue(Double.NaN+!=+Double.NaN);
Assert.IsTrue(Double.NaN.Equals(Double.NaN));|code-block|syntax|javascript|1501584|在同一时间|1501585|Assert.IsTrue(Double.PositiveInfinity+==+Double.NegativeInfinity);
Assert.IsTrue(Double.PositiveInfinity.Equals(Double.PositiveInfinity));
//+same+for+Double.NegativeInfinity+and+Single|1501586|对Double和Single使用静态函数，例如|1501587|Double.IsNaN(value)+&&+Double.IsInfinity(value);|1501588|或者更具体的：|1501589|Double.IsPositiveInfinity(value);
Double.IsNegativeInfinity(value);|1501590|entityMap^0|2|O|0|3|3|8|D|Q|D|0|M|8|0|0|0|0|1|6|8|6|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|J|3|K|5|L|7|1F|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|1G|8|@]|D|@]|E|$]]|$1|Q|3|R|5|L|7|1H|8|@]|D|@]|E|$M|N]]|$1|S|3|T|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|U|3|V|5|L|7|1N|8|@]|D|@]|E|$M|N]]|$1|W|3|X|5|6|7|1O|8|@]|D|@]|E|$]]|$1|Y|3|Z|5|L|7|1P|8|@]|D|@]|E|$M|N]]|$1|10|3|-4|5|6|7|1Q|8|@]|D|@]|E|$]]]|11|$]]

The reason of <code>Double.NaN != Double.NaN</code> is simple:

Do you expect <code>0/0</code> to be the same as <code>Math.Sqrt(-3)</code>? And same as <code>Math.Sqrt(-7)</code>?

There is a bug in C# in my opinion where <code>Equals()</code> is not overridden for NaN.

<pre><code>Assert.IsTrue(Double.NaN != Double.NaN);
Assert.IsTrue(Double.NaN.Equals(Double.NaN));
</code></pre>

At the same time

<pre><code>Assert.IsTrue(Double.PositiveInfinity == Double.NegativeInfinity);
Assert.IsTrue(Double.PositiveInfinity.Equals(Double.PositiveInfinity));
// same for Double.NegativeInfinity and Single
</code></pre>

Use static functions for <code>Double</code> and <code>Single</code>, e.g.

<pre><code>Double.IsNaN(value) &amp;&amp; Double.IsInfinity(value);
</code></pre>

Or more specific:

<pre><code>Double.IsPositiveInfinity(value);
Double.IsNegativeInfinity(value);
</code></pre>

Can someone explain this to me? In C# double.NaN is not equal to double.NaN

<pre><code>bool huh = double.NaN == double.NaN; // huh = false
bool huh2 = double.NaN &gt;= 0; // huh2 = false
bool huh3 = double.NaN &lt;= 0; // huh3 = false
</code></pre>

What constant can I compare to a double.NaN and get true?

Why is double.NaN not equal to itself?

有人能给我解释一下吗？在C#中，double.NaN不等于double.NaNbool huh = double.NaN == double.NaN; // huh = falsebool huh2 = double.NaN >= 0; // huh2 = falsebool huh3 = double.NaN <= 0; // huh3 = false我可以将哪个常量与double.NaN进行比

问为什么double.NaN不等于它自己？
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问为什么double.NaN不等于它自己？EN

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问为什么double.NaN不等于它自己？
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