Some great books and PDFs: The Art of the Meta Object Protocol (available on Amazon) Object-Oriented Programming in COMMON LISP (Keene, also on Amazon)
For Advance mind twisting Lisp, get Paul Graham's OnLisp (available as a downloadable PDF). My brain hurts just trying to figure out some of the macros (and even more advance features) he rolls out: http://www.paulgraham.com/onlisptext.html I would have to say that "The Art of the Meta Object Protocol" is one of the best comp sci books in my collection. Glenn -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ian Eslick Sent: Wednesday, May 14, 2008 2:16 PM To: Elephant bugs and development Subject: Re: [elephant-devel] Query System Hi Daniel, Welcome to the Metaobject Protocol, aka the MOP! There is a rich embedded language for introspecting over and manipulating the class system in lisp that Elephant uses heavily. You could have a procedure extract the and caches the essential information from the class slot definitions into a little structure. You can do this the first time the query system encounters a class, and add a hook into the class instantiation code that invalidates the cache on class redefinition. It's worth diving into it, but it can take awhile to wrap your head around the concepts, not to mention the idiosyncrasies of the MOP. I'm happy to review your proposal offline or online as you prefer. If you look at src/elephant/package.lisp we import symbols selectively from the metaobject protocol package specific to each lisp. The functions you are looking for are: class-slots - return a list of slot-definition-objects Each of the special elephant slots returned by this function is a subtype of the class standard-effective-slot-definition and persistent- effective-slot-definition. Direct slots are representations of the arguments to the defclass form. Effective slots are computed when the class is 'finalized' (i.e. the first instance is instantiated and it's inheritance hierarchy is fully defined). A generic function called slot-definition-using-class dispatches on the type of the effective slot to implement the common-lisp primitive (slot-value obj slotname) The special types you'll care about are: - persistent-effective-slot-definition persistent-p is a predicate on the slot definition that tells you if it is an instance of or subclass of a persistent slot. - indexed-effective-slot-definition (has special slots named: indices and base-class; predicate is indexed-p) - derived-effective-slot-definition (derived from the index slot also contains a slot: fn for determining the value to index on) - set-valued-effective-slot-definition (slot stores a reference to a pset; set-valued-p) - association-effective-slot-definition (association-p; this is complicated so we should handle this as a special case in the query system later) I have accessors to get these slots from the class object such as association-slot-defs, indexed-slot-defs, and persistent-slot-defs. Read metaclasses.lisp for more information on these definitions. If you know an index exists on a class slot, you can simply call (find- inverted-index class-object slotname) to have the system fetch it for you. This should be enough for you to define a structure like: (defstruct class-info classname slotypes) Where slottypes is an alist: - ((slotname . :indexed) (slotname . :persistent) (slotname . :transient)) or something like that. Ian On May 14, 2008, at 1:45 PM, [EMAIL PROTECTED] wrote: > I've digested Ian and Leslie's comments on this thread and think > we're all on the same page now. I've been reading different papers > and other OODBMs in trying to propose a querying syntax and am > pretty close to completing this now. However, I have some doubts for > which I'll need someone's help with, which will allow me to continue > drafting my proposal. > > I believe Ian (if it was someone else, I apologize for not quoting > you) mentioned that we could, as a later phase, introspect the class > and ask for the indices available in order to do some query > optimizations. So my question goes somewhere along those lines and > I'm wondering (please excuse my limited knowledge of Lisp and thank > you for helping my learning curve) if it's possible to obtain the > list of slots and/or slot-accessor functions for a given class. > > Thanks, > Daniel > _______________________________________________ > elephant-devel site list > elephant-devel@common-lisp.net > http://common-lisp.net/mailman/listinfo/elephant-devel _______________________________________________ elephant-devel site list elephant-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/elephant-devel _______________________________________________ elephant-devel site list elephant-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/elephant-devel
