Subject:
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Bug fix for disappearing backslash (was: Re: Disappearing backslash?)
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Newsgroups:
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lugnet.admin.general
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Date:
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Wed, 2 Aug 2006 20:44:18 GMT
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Viewed:
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6236 times
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In lugnet.admin.general, Steve Bliss wrote:
> In lugnet.admin.general, Rene Hoffmeister wrote:
> > E.g. \ldraw\par\ts\s would become ldraw\parts\s too...
> Wow, that's really weird. Ya gotta love PML...
Hmm, that *is* weird. This isn't actually a PML thing, though, but an FTX
thing. The FTX-to-HTML converter runs as a seperate self-contained module;
all PML parsing occurs prior to the FTX-to-HTML conversion.
The backslash in FTX was intended to work with things like [ ] { } < > | _
rather than with letters, and was later replaced by the backtick, which
happens to exhibit the same strange behavior.
This behavior is definitely a bug in Fibblesnork::Text::Munge -- and it
looks like it's been there for 8 years (sorry).
The problem is that the $esc flag isn't being cleared in the s{}{}egx
substitution when a character is encountered that isn't a special character
(`\{}[]_|<>¬), because it's only matching on special characters.
Consequently, the $esc flag is toggled at every occurrence of the backslash
or backtick when it's accidentally used before a letter.
Thus, if you write \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z,
the backslash will show for every other letter, e.g.: bdfhjlnprtvxz, which
is why it's been so perplexingly unpredictable -- it has nothing to do with
the actual letter being escaped.
One way to fix the bug without introducing a gross inefficiency in the
s{}{}egx operation would be to pre-collapse any errant escapements just
prior to executing the s{}{}egx. Something like this:
my $ESCAPERS =
" \\`
| \\\\
";
my $ESCAPABLES =
" \\`
| \\\
| \\\{
| \\\}
| \\\[
| \\\]
| \\\|
| \\_
| <
| >
| ¬
| \s
";
...
s{(?:$ESCAPERS)(?!$ESCAPABLES)}{}go;
This simply removes any \ or ` characters which happen to accidentally
be followed by a character that's not defined as being escapable.
Note: It *may* make more sense, for practical reasons, to actually keep
backslashes in front of letters, instead of removing them, in which case
the following could be done instead:
s{($ESCAPERS)($ESCAPABLES)}{$1$1$2}go;
--Todd
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