Andre van Tonder <xxxxxx@now.het.brown.edu> 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

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