Formal comment #72 (enhancement)

A record-type-length procedure is suggested
Reported by:	Andre van Tonder

Component:	records
Version:	5.91

Pages : 72 
Summary

A record-type-length procedure is suggested. 

Description

An operation is requested that returns the valid range for the field
index argument of the procedures "record-accessor", "record-mutator"
and "record-field-mutable".

Such a procedure would be convenient and useful for more efficiently
writing operations that act on more than one record type. One use case
supported by record-type-length would be a "record-copy" procedure
that can copy an arbitrary non-opaque record value with maximum
efficiency.

Currently, although the length is indirectly available via
(record-type-field-names rtd), this is less convenient and may be
slighly less efficient for the above kind of use case.

Suggestion

E.g., 
  (record-type-length rtd)

RESPONSE:

As the record fields have numerical indices anyway, 
the next draft will use vectors of field descriptors, and
`record-type-field-names' will return an immutable vector of field
names.  With this change, extracting the field names (as well as
determining their count) can be made constant-time operations without
requiring a new procedure.