[TxMt] Crazy idea: scope assertions in regular expressions

Andy Armstrong andy at hexten.net
Fri Nov 23 18:39:38 UTC 2007

I've just attempted to add folding for POD to TM's Perl language  
definition - forgetting that I've already tried it previously. POD  
looks like this:

=head1 A heading

=head2 A sub heading


The =cut always ends the POD. So my patterns look like ^=(?!cut) and  
^=cut\s*$ respectively. That doesn't work because the folding  
mechanism expects a recursive syntax - each opening 'thing' requires  
its own closing 'thing'.

So I was thinking about how the problem could be solved and it  
occurred to me that it'd be interesting to have an extension to  
regular expression syntax that allowed an assertion to be made about  
the matching scope.

Assuming the assertion was called ?^ you could match the text 'foo'  
only in storage.type.sub.perl or entity.name.function.perl with  
something like this:


Generally (?^ <scope re> : <re> ) would allow <re> to match only if  
the current scope name matched <scope re>.

To solve my folding problem the code that scans for folds would have  
to be scope aware - which may not be feasible architecturally.

And I realise that extending RE semantics to grok rich text is a bit  
of a big undertaking - but I thought it was a cute idea :)

Andy Armstrong, Hexten

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