From: Pit Capitain <pit@...>
Date: 2006-07-07T16:47:42+09:00
Subject: Re: Float#==. Legacy?

Matthew Smillie schrieb:
> On Jul 6, 2006, at 16:39, Guillaume Marcais wrote:
> 
>> As far as my experience goes, using Float#== is always an error. Float 
>> should be compared within epsilon because of errors, etc. etc.
> 
> This is something that I'd refer to as a code smell rather than an 
> error.  Floating point numbers can represent and operate on lots of 
> actual numbers with no loss of precision, for a trivial example: 2.0 + 
> 2.0 will always equal exactly 4.0, and any other result from that 
> operation, no matter how small the difference, would be an error.

You have to know a lot about the implementation of floating point 
numbers in order to be able to predict the result of seemingly trivial 
examples:

   0.1 + 0.1 == 0.2  # => true
   0.1 + 0.2 == 0.3  # => false

The only really trivial examples I can think of use small integers. If 
I'm working with those numbers, I wouldn't use floats, though.

Regards,
Pit