Properties of the `objects.fs' model

• It is straightforward to pass objects on the stack. Passing selectors on the stack is a little less convenient, but possible.
• Objects are just data structures in memory, and are referenced by their address. You can create words for objects with normal defining words like constant. Likewise, there is no difference between instance variables that contain objects and those that contain other data.
• Late binding is efficient and easy to use.
• It avoids parsing, and thus avoids problems with state-smartness and reduced extensibility; for convenience there are a few parsing words, but they have non-parsing counterparts. There are also a few defining words that parse. This is hard to avoid, because all standard defining words parse (except :noname); however, such words are not as bad as many other parsing words, because they are not state-smart.
• It does not try to incorporate everything. It does a few things and does them well (IMO). In particular, I did not intend to support information hiding with this model (although it has features that may help); you can use a separate package for achieving this.
• It is layered; you don't have to learn and use all features to use this model. Only a few features are necessary (See section Basic Objects Usage, See section The class object, See section Creating objects.), the others are optional and independent of each other.
• An implementation in ANS Forth is available.

I have used the technique, on which this model is based, for implementing the parser generator Gray; we have also used this technique in Gforth for implementing the various flavours of wordlists (hashed or not, case-sensitive or not, special-purpose wordlists for locals etc.).

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