What are the disadvantages of using ANTLR compared to Flex/Bison?

I've worked on Flex, Bison few years ago during my undergraduate studies. However, I don't remember much about it now. Recently, I have come to hear about ANTLR.

• Would you recommend that I learn ANTLR or better to brush up Flex/Bison?
• Does ANTLR have more/less f开发者_如何学Pythoneatures than Flex/Bison?

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ANTLRv3 is LL(k), and can be configured to be LL(*). The latter in particular is ridiculously easy to write parsers in, as you can essentially use EBNF as-is.

Also, ANTLR generates code that is quite a lot like recursive descent parser you'd write from scratch. It's very readable and easy to debug to see why the parse doesn't work, or works wrong.

The advantage of Flex/Bison (or any other LALR parser) is that it's faster.

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ANTLR has a run-time library JAR that you must include in your project.

ANTLR's recursive-descent parsers are easier to debug than the "bottom-up" parsers generated by Flex/Bison, but the grammar rules are slightly different.

If you want a Flex/Bison-style (LALR) parser generator for Java, look at JavaCC.

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We have decided to use ANTLR for some of our information processing requirements - parsing legacy files and natural language. The learning curve is steep ut we are getting on top of it and I feel that it's a more modern and versatile approach for what we need to do. The disadvantages - since you ask - are mainly the learning curve which seems to be inevitable.