[gambit-list] various

Taylor R Campbell campbell at mumble.net
Wed Nov 5 13:52:25 EST 2008

   Date: Wed, 5 Nov 2008 12:03:19 +0100
   From: "Christoph Bauer" <christoph.bauer at lmsintl.com>

     - is there a way to copy a record (define-structure) or
       to convert it to a list, like table-copy and table->list? for tables

Records are generally used to implement abstract data types that
satisfy no other properties than the ones you endow them.  Unlike
tables or lists, they are not treated as general associations or
sequences of objects; instead they are treated however you designate
them to be treated.  Copying, thus, is a highly application-dependent
notion of which no general implementation can be prescribed.  For
instance, consider the following record type (defined with SRFI 9, but
this detail is irrelevant):

(define-record-type <pare>
  (kons kar kdr)
  (kar kar set-kar!)
  (kdr kdr set-kdr!))

The names were meant to be suggestive of a linked list structure
derived from this record type -- but no machine would infer that a
LYST-COPY routine on these structures would be analogous to SRFI 1's
LIST-COPY.  But then in some cases you will want to copy not just the
structure of a list but the elements of the list to some degree.
Again the machine cannot infer this; you the programmer must supply
this information.

For elaboration on the subject, see Kent Pitman's essay `The Best of
Intentions' at <http://www.nhplace.com/kent/PS/EQUAL.html>.

More information about the Gambit-list mailing list