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From: Hans Hagen <pragma@wxs.nl>
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Subject: Re: xml comments
Date: Tue, 27 Nov 2001 10:43:54 +0100
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At 09:37 AM 11/27/2001 +0100, Taco Hoekwater wrote:
>"Hans Hagen" <pragma@wxs.nl> wrote:
> > At 03:20 PM 11/26/2001 +0100, Patrick Gundlach wrote:
> > >Hi,
> > >
> > >xml comments have a bug (!?): spaces are critical at the
> > >beginning of a comment.
> >
> > you may try (and play with):
> >
> > \long\def\xparseXMLescape !#1#2#3{\parseXMLescape{#1#2}#3}
>
>Adding #3 is safe, sort of. <! is always followed by one of the language's
>keywords, and <!-- is by far the shortest of those. Just watch out
>that <!----> is a valid comment (although very unlikely to appear).
>
>The string "<!-- crap -->" is actually a comment that starts with
>a space. The comment itself in this case is: " crap ".
>
>It is possible to take advantage of the fact that '<!--' is the only
>keyword that starts with the same character twice, so the 'best' thing
>to do is something along these lines:
>
>\long\def\xparseXMLescape!#1#2%
>   {\if#1#2%
>      \@EA\handleXMLcomment
>     \else
>      \@EA\doxparseXMLescape
>     \fi#1#2}
>
>\def\handleXMLcomment--#1-->{}
>
>\def\doxparseXMLescape#1 {\parseXMLescape{#1}}

yesterday i found out that i needed both alternatives , so i came up with:

\long\def\xparseXMLescape !#1#2%
   {\if#1-%
      \if#2-%
        \expandafter\expandafter\expandafter\xxparseXMLescape
      \else
        \expandafter\expandafter\expandafter\xyparseXMLescape
      \fi
    \else
      \expandafter\xyparseXMLescape
    \fi#1#2}

\long\def\xxparseXMLescape --#1{\parseXMLescape{--}#1}
\long\def\xyparseXMLescape #1  {\parseXMLescape{#1}}

so far this one works ok.

indeed, if we assume that #1 and #1 are the same and -, we can have a 
faster alternative, but we may want to play safe. How does this keyword 
mechanism work? Are there only officially registered ones?

Hans
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                                   Hans Hagen | PRAGMA ADE | pragma@wxs.nl
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