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Re: Why vectors?

This page is part of the web mail archives of SRFI 99 from before July 7th, 2015. The new archives for SRFI 99 contain all messages, not just those from before July 7th, 2015.

On Sun, 10 Aug 2008, Derick Eddington wrote:

Why are vectors and not lists used for make-rtd's and rtd-constructor's
fieldspecs arguments and for rtd-field-names's and rtd-all-field-names's
return values?  Is the only reason to follow R6RS's use of vectors?  If
so, I request lists be used instead because they're easier to deal with,
as shown by how much list<->vector conversion is done in the ERR5RS
reference implementation itself.  Using lists instead would increase the
appeal of this SRFI to me, and I think to others also.  IMO,
interoperating with the R6RS records procedures that deal in vectors
without having to convert list<->vector is not a good enough reason
compared to the benefit of using lists with one's primary record system
of use, because interoperating at the procedural level where these
vectors matter will be rare (I imagine).  Or is there a good reason to
use vectors?

Vector referencing is in constant time.  List referencing is in linear time.
Vector mutation is in constant time.  List mutation is in linear time.

As records are essentially vectors (constant sized, fixed order, etc) with
procedures mapping to indices, using lists would be a significant performance
cost for no benefit: one generally doesn't iterate over the elements of a
record.  Record types are for grouping related *but independently used* data