Marc Nieper-Wißkirchen scripsit:

> In order to subtype record-type definitions made by either of these
> specifications such that the subtypes are subtypes in the sense of
> SRFI 137, this SRFI 137 should define an interface that is to be
> implemented by record-type descriptors on systems supporting SRFI
> 137 that gives access to the (underlying/emulated) SRFI 137
> interface of the record-type.
>
> For example, SRFI 137 could specify a syntax ’type’ such that (type
> <rtd>) would expand into the five values of the
> (underlying/emulated) ’make-type’ that was evaluated during creation
> of the record-type.

I don't see how this would work with multiple record systems:  which
one gets to define `type`?  Also, record systems would have to be
extended to be able to create types using this mechanism.

One of the major limitations of Scheme currently is its lack of SPIs
(service provider interfaces) that different modules can plug into.

--
John Cowan          http://www.ccil.org/~cowan        xxxxxx@ccil.org
Statistics don't help a great deal in making important decisions.
Most people have more than the average number of feet, but I'm not about
to start a company selling shoes in threes. --Ross Gardler