[r6rs-discuss] [Formal] Record layers are not orthogonal.

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Submitter: William D Clinger
Email address: will_at_ccs.neu.edu
Issue type: Simplification
Priority: Minor
Component: Records
Report version: 5.91
Summary: Record layers are not orthogonal.
Full description of issue:
The procedural record layer (r6rs records procedural)
is strictly more expressive than the syntactic layers,
(r6rs records explicit) and (r6rs records implicit),
because the procedural layer can create new subtypes
given only a record-type-descriptor, but the two
syntactic layers cannot.
This is entirely appropriate, assuming the syntactic
layers are provided only for convenience in simple
cases, and the procedural layer is intended to be
used for all complex cases.
Assuming that assumption, however, the two syntactic
layers could be simplified further.  Since they are
not intended to be fully general, they ought to be
made easier to use for simple cases.
Although simplification of the syntactic layers is
one solution to this problem, I would suggest a more
radical solution: omit both syntactic layers from the
R6RS.  Both could be described by a SRFI and provided
by portable reference implementations that build on
the procedural layer.
Omitting the syntactic layers from the report would
have the added benefit of permitting other syntactic
alternatives on an equal footing with those described
in the draft R6RS.  No portability would be lost; the
procedural layer would be the only universal record
layer, just as in the draft R6RS.
[end of comment]