From: Sean O'Dell <sean@...>
Date: 2004-06-26T04:21:41+09:00
Subject: Re: Is it considered Harmful?

On Friday 25 June 2004 12:13, Charles Comstock wrote:
> Sean O'Dell wrote:
> > On Friday 25 June 2004 09:15, ts wrote:
> >>>>>>>"S" == Sean O'Dell <sean@celsoft.com> writes:
> >>
> >>S> It should be very easy to do.  I'm wondering if a C extension could
> >>possibly S> even do this.
> >>
> >> You are right, a C extension can effectively crash ruby
> >>
> >> Read carefully hash.c and array.c and just imagine what will be the
> >> result if one method of hash.c will be applied to an array.
> >>
> >> matz has one day say it in a message to ruby-talk : one information is
> >> missing
> >
> > You can do all sorts of things with Ruby, I see no reason why changing an
> > object's class would crash Ruby anymore than, say, redefining a method to
> > something different than an object expects, or including modules in a
> > class that don't belong there.  Just be careful of what you're doing.  I
> > see no FUNDAMENTAL reason why you couldn't change an object's class.
> >
> > 	Sean O'Dell
>
> All of those places that you can assume the underlying datatype hasn't
> changed result in increased performance for us because there is no need
> to double check the type.  If you have #class= then you would have added
> overhead on a significant portion of the code for a small use case.
> While this isn't a fundemental reason it is a logical reason why it may
> have been avoided in the first place.  Why don't you try and make a
> patch that allows this on your own copy and compare performance and the
> like?

Actually, the comparison is a function call that mostly just checks a bit 
mask.  That's overhead, but fairly minimal I think.

	Sean O'Dell