有人可以用Ruby向我解释NaN吗？

I just found a bug in some number manipulations in my program and I'm getting a FloatDomainError (NaN)

我刚刚在我的程序中发现了一些数字操作的错误,我得到一个FloatDomainError(NaN)

So I started logging the number passed in with:

所以我开始记录传入的号码:

if(metric.is_a?(Numeric))
  self.metric = metric
else
  LOGGER.warn("metric #{metric} is not a number")
  self.metric=0
end

But the number being passed in is NaN which apparently is_a?(Numeric) as I don't get my log warning, and it passes metric on to my metric= method, which is where I get my FloatDomainError

但传入的数字是NaN,显然是__?(数字)因为我没有得到我的日志警告,它将度量传递给我的metric =方法,这是我得到我的FloatDomainError的地方

Now, correct me if I'm wrong, but doesn't it seem semantically wrong to have an NaN (Not A Number) be of type Numeric ?? Can someone explain this to me?

现在,如果我错了,请纠正我,但是如果NaN(非数字)是Numeric类型,那么在语义上是否错误?谁可以给我解释一下这个?

BTW using Jruby-1.4.1

BTW使用Jruby-1.4.1

2 个解决方案

#1

IEEE 754 floating point numbers define -INFINITY +INFINITY and NotANumber to make it possible to react to lets say division by zero. you can also calculate with these for eg 2 + INF = INF

IEEE 754浮点数定义-INFINITY + INFINITY和NotANumber以使得可以做出反应,假设除以零。你也可以用这些来计算例如2 + INF = INF

NaN isn't a uniqe ruby feature, they are numeric in java, c++, ... too

NaN不是一个独特的ruby功能,它们在java,c ++等中也是数字

#2

I think that making NaN a number makes perfectly sense...

我认为让NaN成为一个数字非常有意义......

try 0.0 / 0.0 in irb -> the result is NaN (which in this case is infinity)

在irb中尝试0.0 / 0.0 - >结果是NaN(在这种情况下是无穷大)

Infinity is mathematically kind of a number, but still, you can't express it with a datatype... in math you use a special symbol too...

Infinity在数学上是一个数字,但是,你仍然不能用数据类型来表达它......在数学中你也使用了一个特殊的符号......

PS: You can use metric.nan? to check it... then it should work as you expect...

PS:你可以使用metric.nan?检查它...然后它应该按预期工作...

#1