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Example problem: I want to write a Haskell script that will highlight (e.g. with \fbox) the first occurrence of mathematical symbols in a document. Hopefully, this will help me ensure that I've introduced everything.

  • Regex's are inappropriate, since they won't know what's in math mode, etc., and don't have the logic to count things, or know that a variable from the next \section is actually a new variable.

  • I also don't want to write a parser for all LaTeX. It seems the probability of mistakes is high, and I really just want to write a script, not a commercial program.

I wrote a mixed parser -- one that got some structure, and kept the rest as text, in a response to a question here. [ How do you use parsec in a greedy fashion? ]. But, my approach was cumbersome. Is there a better, more formal way?

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gatoatigrado
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    Don't be too hasty to discount regex - remember regex are almost always embedded in a full programming language (e.g. Haskell in this case) that can count, perform choice etc. As I mentioned in the other question, what you are looking for is "island parsing" but Haskell has no tools for this and if you try to do it with regular "parsing" rather than regex-matching you immediately have problems recognizing start and end symbols to enter and leave the parsing islands. – stephen tetley Nov 20 '11 at 14:48

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You might want to take a look at the Pandoc library on Hackage for parsing Latex. It will let you parse, modify, and pretty print Latex as well as a bunch of other formats.

Anupam Jain
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