ExplicitPatternGroup LookBehind Equivalent?

SyntaxEditor for Windows Forms Forum

Posted 15 years ago by Marianne
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I have several language defs with a bunch of keywords...nothing unusual there. My problem is that if I have a keyword 'left', I only want it to be considered a keyword if it's not preceded by a period character. There is no lookbehind option in the explicit pattern group so how do I differentiate:
Left("my string", 3) (should be a keyword)
SomeObject.Left (should not be a keyword)

------------------------------- Marianne

Comments (5)

Posted 15 years ago by Actipro Software Support - Cleveland, OH, USA
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This was requested by another customer as well for the VB language. Right now there's no really good way to handle that since there is no look-behind. We do want to implement look-behind soon. However even if we have it, we need a way to assign a common look-behind to a lexical pattern group, like a group of keywords. Do you think we should also add a LookBehind attribute similar to our LookAhead attribute in the lexical pattern group itself that would apply to all inner keywords?


Actipro Software Support

Posted 15 years ago by Marianne
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Quote:
<font size="1" face="Verdana, Arial">quote:</font><HR>Do you think we should also add a LookBehind attribute similar to our LookAhead attribute in the lexical pattern group itself that would apply to all inner keywords?<HR>
That is exactly how I was thinking it could be handled. Obviously, this is something that should work for both explicit and regex pattern groups. But in my example, adding LookBehind=[^\.] should prevent the keyword from being recogized if it was preceded by a period.

------------------------------- Marianne

Posted 15 years ago by Boyd - Automated Software Testing Consultant / Developer, Patterson Consulting, LLC
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I've been feeling the pain of this as well, and I think you have the right idea. Adding a complement to the "LookAhead" attribute for Explicit and RegEx groups should do the trick.
Posted 15 years ago by NSXDavid
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I have the same issue, and I sorta solved it by defining a token that consists of whitespace followed by the text to distinguish it. That solution is not very robust and messes up the visuals on collapse and so forth.

-- David
Posted 15 years ago by Marianne
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That won't work, though, for a large group of explicit patterns, but I agree it would work for regex patterns.

------------------------------- Marianne

The latest build of this product (v2018.1 build 0342) was released 11 days ago, which was after the last post in this thread.

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