From: Robert Klemme <shortcutter@...>
Date: 2009-04-30T04:35:06+09:00
Subject: Re: Detecting -0.0

On 29.04.2009 17:39, Jeff Schwab wrote:
> Robert Klemme wrote:
>> On 28.04.2009 22:27, Jeff Schwab wrote:
>>> Thomas B. wrote:
>>>> Hello.
>>>>
>>>> I have a simple question - how to detect if a variable contains a Float
>>>> of value -0.0? Is there any special method for this, or any comparison
>>>> that distinguishes negative zero from a the regular zero?
>>>
>>> NB: I'm not sure how portable this is.
>>>
>>> def negative_zero?(number)
>>>   inverse = 1 / number.to_f
>>>   inverse < 0 && inverse.infinite? ? true : false
>>
>> Why do you use the ternary operator to convert a boolean into a boolean?
> 
> I don't.  Float#infinite? can return nil, -1, or +1, but never true or 
> false. Without the ternary, the original client code produces the 
> following, far less meaningful output, including the blank line:
> 
> false
> -1
> 
> false

Well, but all these are perfectly boolean values in Ruby.  There is no 
need to convert the expression other than for display maybe.  But in 
that case I'd do the conversion outside the method as it does not add 
any semantics to the method implementation but costs time.

Kind regards

	robert

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