You can put it there, yes.
But there is an important design question lurking there. If you put the unification method on these classes, what you are really saying is: this Smalltalk object can be unified with that Smalltalk object. So you are then extending the Smalltalk language with unification.
The alternative is to only have unification methods un your own 'unifiable objects' hierarchy. In that hierarchy you will probably have a class called: CWNumber, which represents numbers in your language and which will hold a Smalltalk number.
Which alternative to choose depends on whether, and how deep, you want to integrate Smalltalk and your own language. Unless you really want to mingle Smalltalk objects within your language, or want unification directly accessible at the Smalltalk level without having to pass through your language, I would advise the second option.
( If you are interested I have a number of papers I can point you to, since I did research on integrating a Prolog in Smalltalk )
On 16 Feb 2007, at 16 February/06:34, Chris Wright wrote:
I would like to play around with some classes which require unification (I know about Prolog/V etc...). I am not sure where to "put" the unification algorithm.
It might look like:
anObject unifiesWith: anotherObject in: anEnvironment
? does that seem like the right sort of selector?
So, to I put that in Number, Strings, Array, (and a class I've made
- LogicVar)?
Is it "OK" to extend the functionality of the built-in classes this way, or should I derive my own Number, String, Array --- I want to use the parser/compiler that Squeak already has, so I want to be able to enter:
5 unifiesWith: 5 in: emptyEnv
On the subject of return values, what's the best way to return more than one value? Should I create my own class (UnificationReturnValue) (then I could tell it how to respond to ifTrue/ifFalse etc), or should I return a collection with indexes for the success-value and the environment-value?
Thanks!
Cheers
Chris
-- A/Prof Chris Wright FJFICJ FRACP MBBS Medical Director, ICU Monash Medical Centre Clayton, VIC _______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners