regexp and valid-sre? Michael Montague (26 Nov 2013 03:34 UTC)
Re: regexp and valid-sre? Alex Shinn (26 Nov 2013 12:44 UTC)
Re: regexp and valid-sre? Peter Bex (26 Nov 2013 14:25 UTC)
Re: regexp and valid-sre? Michael Montague (26 Nov 2013 18:00 UTC)
Re: regexp and valid-sre? Peter Bex (26 Nov 2013 18:21 UTC)
Re: regexp and valid-sre? Michael Montague (26 Nov 2013 19:09 UTC)
Re: regexp and valid-sre? John Cowan (26 Nov 2013 18:24 UTC)
Re: regexp and valid-sre? Michael Montague (26 Nov 2013 19:17 UTC)
Re: regexp and valid-sre? Peter Bex (26 Nov 2013 19:23 UTC)
Re: regexp and valid-sre? Kevin Wortman (26 Nov 2013 19:52 UTC)
Re: regexp and valid-sre? Michael Montague (26 Nov 2013 19:59 UTC)
Re: regexp and valid-sre? Kevin Wortman (27 Nov 2013 23:33 UTC)
Re: regexp and valid-sre? John Cowan (27 Nov 2013 23:42 UTC)
Re: regexp and valid-sre? Arthur A. Gleckler (30 Nov 2013 14:55 UTC)
Re: regexp and valid-sre? Michael Montague (26 Nov 2013 18:02 UTC)
Re: regexp and valid-sre? John Cowan (26 Nov 2013 18:19 UTC)
Re: regexp and valid-sre? Michael Montague (26 Nov 2013 19:11 UTC)

Re: regexp and valid-sre? Peter Bex 26 Nov 2013 18:19 UTC

On Tue, Nov 26, 2013 at 10:00:10AM -0800, Michael Montague wrote:
> I don't think that these are strong arguments for having 'valid-sre?'.
> An implementation for which compiling is expensive, could easily
> internally do the "is it valid"-type check before compiling. Having it
> in the interface adds no functionality that is not already easily available.

You're missing the part where I said "on-the-fly".  If it _is_ valid,
this will be unacceptably slow if you're only interested in providing
feedback to the user whether their currently entered expression is
valid or not.  I don't think this feature is far-fetched: programs
like RegexBuddy do this, and an enhanced Scheme IDE could also do
something like that.

The valid-sre? test is more primitive, and it doesn't make sense to
wrap this up in the constructor, requiring people to create a complete
regex object (with the overhead and memory garbage it creates) just
to get at this information is a bad idea.

Cheers,
Peter
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