Well, the pentiumpro optimised binary gives this:

[root@localhost scott]# ruby -e 'p ((13.4 % 1 - 0.4).abs)'
3.330669074e-16

-Scott-

> float 9 .. Hmm, could you show me the result of
>
>   ruby -e 'p ((13.4 % 1 - 0.4).abs)'
>
> OK?
>
>                                                         matz.