Ensuring class x is a superclass of class y

This is a general CL question (although it's MOPpy and I need the answer to work in LW).

I have a metaclass, soa-class, which has some additional behaviour from standard-class.  There is a class, soa, which is an soa-class, but whose direct superclass is standard-object.  soa needs to be a superclass of any soa-class, except itself.

What I currently do is have methods on validate-superclass which will succeed if both classes are soa-classes, but will succeed if the superclass is a standard-class and the subclass is an soa-class only if the subclass is named soa.

This achieves what I want, but it also does something much stronger: if an soa-class has superclasses x, y, ... z then *all* of these must be soa-classes.  So I can't use mixin classes which are not themselves soa-classes.  That's stronger than I need or want.

What is the appropriate way to ensure that, in the above case, at least one of x, y ... z is an soa-class?  Is the superclass argument to validate-superclass finalized enough that I can check its precedence list?

--tim

(Sigh.  Every time I use the CLOS MOP I realise how lucky we are they didn't try to standardise it as part of CL: the language never would have been standardised if they had.  It's just made of jelly, and language standards made of jelly are not a good idea.  Although they can be nutritious.)



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