Treetop: Grammar’s Cool
Tuesday, February 12th, 2008Treetop was one of the more exciting projects I saw at last year’s RubyConf. Nathan Sobo’s Treetop talk is available online and I urge you to watch it. Nathan did a great job of explaining the basics of syntactic analysis, and then got into the specifics of using Treetop’s implementation of parsing expression grammars to put the concepts to work.
Treetop appeared to gather all the concepts together into an understandable domain specific language. All of the tokenization and node structure can go into a single file, and the interactive nature of Ruby makes for the perfect sand box. I felt like I could get somewhere if I invested just an hour into this. I was happy to find that my impressions were correct.
After a short time I had caught on enough to start writing my own code. Once over the hump the rest was easy. I was able to write and test a Treetop grammar for parsing CSV files within a few hours. I chose CSV parsing because I was already familiar with the format, and I could compare my implementation to not just one but two existing Ruby libraries.
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