From: Matthias Reitinger <reitinge@...>
Date: 2009-04-29T05:17:27+09:00
Subject: Re: Detecting -0.0

Joel VanderWerf 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?
>> 
>> Thanks in advance.
>> TPR.
> 
> irb(main):001:0> x = -0.0
> => -0.0
> irb(main):002:0> x == 0.0
> => true
> irb(main):003:0> x.eql?(0.0)
> => true
> irb(main):004:0> x.equal?(0.0)
> => false

  irb(main):001:0> x = 0.0
  => 0.0
  irb(main):002:0> x == 0.0
  => true
  irb(main):003:0> x.eql?(0.0)
  => true
  irb(main):004:0> x.equal?(0.0)
  => false

In short: you cannot distinguish between 0.0 and -0.0 this way.

-Matthias
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