From: Hal Fulton <hal9000@...>
Date: 2004-10-28T05:32:18+09:00
Subject: Re: Rounding error, (100.0 * 9.95).to_i == 994

Dan Janowski wrote:
> I would agree if it were not for this:
> 
> $ ruby -e 'puts (100.0*9.95).to_s'
> 995
> $ ruby -e 'puts (100.0*9.95).to_i.to_s'
> 994
> 
> Ruby seems to be able to manage the FP error rate since FP.to_s show the 
> exact value. Why shouldn't to_i benefit?
> 
> It seems to me that this type of intolerance would effectively make to_i 
> not only worthless but dangerous.

I sympathize, but I think the point is this:
   - to_i doesn't round, it truncates;
   - you have #round if you want to use it;
   - to_s has to either round or truncate; rounding
     seems logical
   - therefore expr.to_s and expr.to_i.to_s may differ

It's a matter of opinion, but I think it's working properly.
Just another of hundreds of design issues Matz has faced.


Hal