Re: [Scheme-reports] Inconsistency of sequence copying procedures

[John Cowan <cowan@x>]

Marc Feeley scripsit:

> Vectors and bytevectors have a similar external representation, yet
> bytevectors are self evaluating (page 46) and vectors are not self
> evaluating.  I do not care very much if they are, or if they are not
> self-evaluating, but it should be the same for vectors and
> bytevectors.

Both are now self-evaluating.

> 2) sequence copying procedures inconsistencies

Things have changed in this area since draft 6 due to the fifth ballot;
in addition, there is an outstanding ticket for the sixth ballot.  So I'll
summarize the current situation.

Subsequence extractors:

  (list-copy list) ; WG rejected adding further arguments
  (string-copy string [start [end]]) ; per SRFI 13; WG rejected fill
  (substring string start end) ; backwards compatibility with R5RS
  (vector-copy string [start [end [fill]]]) ; per SRFI 43
  (bytevector-copy bytevector)
  (bytevector-copy-partial bytevector start end)

  ;; Ticket #384 merges the last two as:
  (bytevector-copy bytevector [start [end]])

Mutating copiers:

  ;; WG rejected list-copy! as insufficiently useful
  (string-copy! to at from [start [end]])
  (vector-copy! to at from [start [end]])
  (bytevector-copy! to at from [start [end]])

> I do not see a good reason for having different APIs (mix of required
> and optional parameters) and naming conventions for similar operations.

The WG voted for consistency with SRFI 1, SRFI 13, and SRFI 43 rather than
complete self-consistency.  However, things are much more consistent now,
especially if #384 passes.

> The naming convention could be based on the one which has been in
> place for strings for a long time, i.e. substring, subvector, and
> subbytevector for extracting subsequences.

"Subblob" was informally rejected by WG as too ugly, and the
"subvector" and "subbytevector" were never suggested.

> Finally, I think the handling of the fill parameter is questionable.
> It is a bad idea for the fill parameter to have a default.

This comes from SRFI 43, but your argument is reasonable and does not
break backward compatibility.  Ballot ticket #450 filed.

-- 
John Cowan    cowan@x    http://ccil.org/~cowan
Nobody expects the RESTifarian Inquisition!  Our chief weapon is
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