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Re: [Scheme-reports] 6.4 control features: -map and -for-each procedures
- To: Andy Wingo <wingo@x>
- Subject: Re: [Scheme-reports] 6.4 control features: -map and -for-each procedures
- From: John Cowan <cowan@x>
- Date: Sat, 21 May 2011 17:09:54 -0400
- Cc: scheme-reports <scheme-reports@x>
- In-reply-to: <email@example.com>
- References: <firstname.lastname@example.org>
Andy Wingo scripsit:
> Right, control features. I already mentioned the
> multiple-return-from-mapping proc issue before. There are three
> options that I am aware of:
> 1) Ignore the issue.
> 2) Specify that a second return from a mapped procedure cannot
> affect the data structure returned by the first return. Effectively
> prohibits the build-it-backwards-and-reverse-in-place idiom, though
> you may reverse and form a new list.
> 3) Specify that it is an error to return multiple times.
I have filed a ticke for choice 3. I don't see that anyone will want 2,
especially for string-map and vector-map.
> Suggestion: that it be an error for a mapped procedure to mutate the
> list being mapped.
> Also, what is the motivation for having multi-arg `map' terminate at
> the first empty list?
Compatibility with the widely accepted SRFI 1.
> 5) You'd need blob-map to be complete, for this report...
Ticket filed to complete blob.
> Suggestion: remove vector-map, string-map, and their for-each
> procedures from the WG1 report.
The WG1 charter says: "Self consistency is an important objective,
which may require adding new features."
John Cowan <cowan@x> http://www.ccil.org/~cowan
Raffiniert ist der Herrgott, aber boshaft ist er nicht.
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