February 27, 2004

The state of parrot objects

If you've been hanging out on perl6-internals you probably know, but if you haven't and actually care, here's a quick rundown of where Parrot's object system stands right now. Note that this is not the final state, just the state we're in and will be for the 0.1.0 release.

At the moment you can:


  1. Create a class
  2. Subclass a class
  3. Have multiple parents for a class
  4. Have attributes1 for a class
  5. Instantiate objects of a class
  6. Call methods on an object with hierarchy searching

What doesn't work:

  1. Adding attributes to a class that's been subclassed
  2. Adding parents to a class that's been subclassed
  3. Adding attributes to a class that's been instantiated
  4. Adding parents to a class that's been instantiated
  5. Fallback methods (i.e. AUTOLOAD or other "Maybe this one will work methods)
  6. Multimethod dispatch
  7. Objects acting like regular PMCs (no vtable overrides). So no operator overloading or tie stuff yet.
  8. Subclassing non-ParrotClass based classes (like Array, Null, or any other PMC class)
  9. NEXT2 and SUPER3 dispatching

Namespaces are also a bit dodgy, though not too bad. (Just don't use multi-level namespaces right now) There's no method cache yet, so things'll be a bit slow for right now. And IMCC has no syntax to support objects so you've got to manage it all by hand at the moment, though it's really not too bad. Details of the system are in PDD 15 if you're so inclined, though not everything that's documented in there currently works. (And there are, I'm sure, things that aren't in there that need to be)

With this release I think we've vaulted parrot firmly into the mid-'80s. (Alas not the early '70s, since OO stuff seemed to go firmly backwards for a few decades from the high-water mark that Smalltalk set, but we're getting there) More of the missing stuff, especially AUTOLOAD and operator overloading/tying, should be in 0.1.1, but we'll see where that goes.

1 Or, as .NET calls 'em, properties. (I think. Maybe not, opinions vary) Object slot variables. Class-private "every object of this class has this thing in it" things.
2 Which continues the method search as if the method that was actually invoked didn't exist
3 Which continues the method search as if the class the method that was invoked is in is the base class for the object

Posted by Dan at February 27, 2004 10:27 AM | TrackBack (2)
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