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On Fri, 31 Mar 2006, Ryan Allen defenestrated me:
> 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
>
>
> 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?

Looking at some IEEE spec will explain this in agonizing detail, but
simply stated numbers in a computer are stored in a base 2 format. The
math you are doing is base 10. Not all base 10 values can be perfectly
represented in base 2. This can cause calculations to not quite come
out right.

A book on numerical analysis can also be a good intro on this stuff.

-Tom

--
+ http://www.tc.umn.edu/~enebo +---- private.php?do=newpm&u= ----+
| Thomas E Enebo, Protagonist | "Luck favors the prepared |
| | mind." -Louis Pasteur |

Thank you for the replies!

I should have searched the list first before asking!

Ryan.

Just to corroborate: I actually do prefer RHEL distros, but the Ruby
RPM's should be avoided.

On Thursday 30 March 2006 05:21 pm, wrote:
> On Fri, 31 Mar 2006, Randy Kramer wrote:
> > On Thursday 30 March 2006 12:59 pm, wrote:
> if you follow these steps just about anything will work:
>
> - chose a common nfs location. we'll call it /nfs
>
> - every single time you compile something do this
>
> export LD_RUN_PATH=/nfs/lib
> export LD_LIBRARY_PATH=/nfs/lib
> ./configure --prefix=/nfs && make && make install
>
> i set LD_LIBRARY_PATH and LD_RUN_PATH in my .bashrc because i do this
> so much. the cool thing with LD_RUN_PATH is that it __encodes__
> inter-library dependancies (so ruby tk.so needs libtk.so needs ...) such
> that users do not need to set LD_LIBRARY_PATH themselves. of course they
> may, but they do not have to
>
> - all users of code on this partiion need only do
>
> export PATH=/nfs/bin:$PATH
>
> i have a /nfs/build and /nfs/packages - you can guess what these are for
> if you like this approach you may want to check out gnu stowe. i find
> it easy enough to do by hand though...

Thanks very much! I haven't tried this yet, but it looks like it should solve
a lot of my problems.

Randy Kramer