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Re: RFC: Adding \p{foo=/re/}

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From:
Tony Cook
Date:
February 6, 2019 00:51
Subject:
Re: RFC: Adding \p{foo=/re/}
Message ID:
20190206005016.7my35lysjnizdkdn@mars.tony.develop-help.com
On Tue, Feb 05, 2019 at 05:33:23PM -0700, Karl Williamson wrote:
> Although it's called a technical standard, it's not actually a part of the
> Unicode Standard, and even though those clauses are written as if they are
> requirements, they're not.
> 
> This was made clear to me when we followed this document closely, and then
> Unicode made a contradictory rule in the actual Standard.  When I pointed
> this out, they (did seem to be embarrassed, and) said UTS 18 isn't a
> standard, and they removed the language from it, leaving us in the lurch.
> There was a deprecation period for people who were using what we had
> furnished, before we fully supported the Standard again.
> 
> The lesson here is that Unicode doesn't always know best, and we need to
> exercise judgment in following them.  Various things from this document have
> been withdrawn as a result of my and others questioning them.  One I noticed
> again today is 2.1, where there there used to be an RL2.1 apparent
> requirement.  This document appears to have been written by a bunch of
> people sitting around and brainstorming what would be nice, but without an
> implementation to test things out on.
> 
> We already differ significantly from their syntaxes.  Our set notation is
> different; we don't have a \p{name=...} syntax, etc.
> 
> I knew that they thought the patterns weren't anchored, but my experience
> indicates we should do what we think is best in this regards, which may be
> the unanchored approach.  But I want to hear what people think from a
> perl-based view.

From a perl POV, I think it should still be unanchored, since the
syntax is that of a regexp.

I expect both anchored and unanchored to be about as useful as the
other, but I suspect you have a better understanding of the possible
range of value for Unicode properties.

If we're not that worried about following TR18 we could change the
syntax some more to \p{foo=~/.../}

Tony

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