From: Ryan Allen <ryan@...>
Date: 2006-03-31T08:58:16+09:00
Subject: Very interesting Float comparison!

Hi Guys (and Gals!)

This is my first post on the list, so Hello!

Something very strange is happening (as far as I can tell) with a  
float comparison; here is the code in question:

("55.59".to_f / 100) == 0.5559    # returns false

However:

"55.59".to_f / 100    # returns Float 0.5559
0.5559                # returns Float 0.5559
0.5559 == 0.5559      # returns true

And more!:

("55.5".to_f / 100)  == 0.555     # returns true
("55.53".to_f / 100) == 0.5553    # returns true
("55.56".to_f / 100) == 0.5556    # returns true
("55.58".to_f / 100) == 0.5558    # returns true
("55.59".to_f / 100) == 0.5559    # returns false !!
("44.59".to_f / 100) == 0.4449    # returns true  !!
("44.59".to_f / 100) == 0.4449    # returns false !!!!

It doesn't seem to like .59's... What did .59 ever do?

I picked this up while writing a unit test, I've run this code in irb  
and I'm not sure what's going on...

Can anyone shed some light on this?

I'm using ruby 1.8.4 (2005-12-24) [powerpc-darwin8.5.0]

Cheers,
Ryan.