Re: Programmer-defined data types, version 2

[Pavel.pa@xerox.com]

Concerning Andy's two points.

External representation:  This is not as easy to solve as you might
initially think.  Note that the ``type-name'' has no semantic import
whatsoever; in particular, it is not guaranteed to be different from all
other type-name's in the system.  Record-type descriptors are
(purposefully) entirely anonymous values; thus, there is no way to map a
type-name back into a descriptor and so no way for the reader to deal with
a syntax of the form #{ "TYPENAME" ... }.

Adding fields to records or record-types dynamically:  This seems to me an
interesting facility that could be built on top of the primitives
described.  I'm very concerned that we not hair up this very simple
functionality with extras that can be built on top of what's already here;
such extras should be added to the library and experimented with by the
community.  The records facility is not intended to be an object-oriented
facility; it captures exactly one simple notion: tuples with a fixed set of
named components.

	Pavel