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Andre van Tonder <andre@xxxxxxxxxxxxxxxxx> writes: > To overcome these objections, I propose the following: > > - Essentially keep the SRFI-9 semantics for define-record-type > (with a small modification below). All types introduced > this way are disjoint and there is *no* subtyping. > - Farm off the polymorphism to a new form, define-record-class > (or perhaps define-record-interface, according to taste). Are you aware of Scheme48's generic dispatch system? I'm not sure whether it's exactly what you want, but it gets close: -- Macro: define-simple-type typename (supertype ...) predicate Here, you probably want to use SRFI-9 type names instead of the predicate. Then, Scheme48 allows to define methods based on a generic procedure: -- Macro: define-generic proc-name method-table-name -- Macro: define-method method-table prototype body Again, probably not _exactly_ what you want, but close. I thought I'd make you aware of these. The source for these are in scheme48/scheme/rts/method.scm Greetings, -- Jorgen -- ((email . "forcer@xxxxxxxxx") (www . "http://www.forcix.cx/") (gpg . "1024D/028AF63C") (irc . "nick forcer on IRCnet"))