Re: draft-klensin-unicode-escapes-02.txt

Philip Guenther <guenther+ietf@sendmail.com> Tue, 20 February 2007 00:36 UTC

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Date: Mon, 19 Feb 2007 17:36:30 -0700
From: Philip Guenther <guenther+ietf@sendmail.com>
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Subject: Re: draft-klensin-unicode-escapes-02.txt
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On Mon, 19 Feb 2007, Frank Ellermann wrote:
...
> For 5.3 (perl) I don't know the correct syntax, if it's like 5.2:
>
>  UNICODEPOINT = %x5C.78 "{" 2*6HEXDIG "}"  ; starts with "\x"

That looks good to me.  Perl accepts values that don't match that syntax, 
but we don't want to get into trying to define perl's corner cases (or, 
indeed, those of *any* language not originally defined by RFC).  This 
should be a 'generate' syntax, not an 'accept' syntax, IMHO.


> If the x is case insensitive it's simply:
...


The 'x' is case sensitive in perl.  \X has no meaning in plain strings, 
but in regexps it is a built in pattern of sorts.  To quote the 
perlunicode(1) manpage:

        o   The special pattern "\X" matches any extended Unicode
            sequence--"a combining character sequence" in Stan-
            dardese--where the first character is a base character
            and subsequent characters are mark characters that
            apply to the base character.  <...>


Philip Guenther