RFC: Class::Moebius

A mathematician confided
That the möbius band is one sided.
You'll have quite a laugh
If you cut one in half,
'Cause it stays in one piece when divided.

I had an idea for a joke module, that provides möbius objects: inside out objects that are also not inside-out. However, thinking more about it, I can see that this could have practical uses.

Imagine the scenario of refactoring in-house modules for inside outedness. The modules themselves could be refactored to use Class::Std, Object::InsideOut, Class::InsideOut or whatever, but lots of existing legacy code could break if it is relying on de-encapsulation ->{foo} syntax.

Möbius objects could provide a migration path allowing the legacy code to still work, albeit generating warnings whenever encapsulation is violated, but still working.

Inside out objects tend to be implemented as a blessed scalarref, using the address or some other unique low level property (their values are not actually used). The möbius object could still use this address, but be a blessed, tied hashref or arrayref. The tie mechanism will intercept any attempts to access attributes directly, and will do the right thing, generating warnings as necessary.

What do others think? Is this idea worth pursuing? Or should it retain "joke module" status?

--

Oh Lord, won’t you burn me a Knoppix CD ?
My friends all rate Windows, I must disagree.
Your powers of persuasion will set them all free,
So oh Lord, won’t you burn me a Knoppix CD ?
(Missquoting Janis Joplin)

Comment on RFC: Class::Moebius

Replies are listed 'Best First'.
Re: RFC: Class::Moebius by xdg (Monsignor) on Jan 11, 2006 at 12:59 UTC
You've just described what jdhedden dubbed "foreign inheritance". Both Class::InsideOut and Object::InsideOut already support this, though in slightly different ways. The former offers it directly; the latter uses a delegation pattern for a more generalized approach. Docs for both give examples. And neither uses `tie`. I've written File::Marker to go along with the inside-out tutorial I'm giving next week at Perl Seminar NY. It gives a very simple example of using the inside-out technique to extend IO::File. Here's a couple threads on the topic as well How to use Inheritance with Inside-Out Classes and Hash Based Classes Inside-out objects inheriting from hash-based classes -xdg Code written by xdg and posted on PerlMonks is public domain. It is provided as is with no warranties, express or implied, of any kind. Posted code may not have been tested. Use of posted code is at your own risk.	[reply] [d/l]
Re: RFC: Class::Moebius by robharper (Pilgrim) on Jan 12, 2006 at 09:43 UTC
I think you should consider the possibility of extending your mobius module into a klein bottle module. I'm not sure if this 3d functionality should be rolled into your initial work or outside it -- perhaps there is no difference. Rob	[reply]
Re^2: RFC: Class::Moebius by rinceWind (Monsignor) on Jan 12, 2006 at 12:09 UTC
It takes 2 dimensions minimum in order to have an outside and an inside - hence möbius. If you can think of an analogy or use for the third dimension, we could well have Class::Klein. By the way, the limerick has another stanza: A mathematician called Klein Thought the möbius band was divine. He said "If you glue The edges of two, You'll get a strange bottle like mine." -- Oh Lord, won’t you burn me a Knoppix CD ? My friends all rate Windows, I must disagree. Your powers of persuasion will set them all free, So oh Lord, won’t you burn me a Knoppix CD ? (Missquoting Janis Joplin)	[reply]
Re: RFC: Class::Moebius by chromatic (Archbishop) on Jan 12, 2006 at 07:29 UTC
It sounds valuable to me. I like the idea of warning on dubious constructs, even if UNIVERSAL::isa and UNIVERSAL::can demonstrate how difficult it can be.	[reply]
Re: RFC: Class::Moebius by TomDLux (Vicar) on Jan 11, 2006 at 18:57 UTC
Terry Pratchett would be proud of you. -- `TTTATCGGTCGTTATATAGATGTTTGCA`	[reply]
Re^2: RFC: Class::Moebius by pajout (Curate) on Jan 12, 2006 at 09:36 UTC
...the best discworld's programmer :>)))	[reply]
Re: RFC: Class::Moebius by rrwo (Friar) on Feb 18, 2006 at 14:48 UTC
The idea is worth pursuing. But it's already been done. I wrote Class::Tie::InsideOut to do just that-- while completely unaware of this thread. (I posted something on London.pm was was sent a link to this.) It works by using tied hashes to link hash keys to variables in the class namespace, and it enforces encapsulation by only letting methods use keys when there is a variable in the same namespace.	[reply]
A reply falls below the community's threshold of quality. You may see it by logging in.