Version 4 of ANother Tool for Language Recognition (ANTLR), a flexible lexer/parser generator. ANTLR4 features an enhanced adaptive LL(*) parsing algorithm, that improves on the simpler LL(*) algorithm used in ANTLR3.
ANTLR stands for ANother Tool for Language Recognition, a powerful parser generator for reading, processing, executing, or translating structured text or binary files. At its core, ANTLR uses a grammar, with syntax loosely based on Backus–Naur_Form, to generate a parser. That parser produces easily traversable parse trees, which can be processed further by the user. ANTLR's simplistic and powerful design has allowed it to be used in many projects, from the expression evaluator in Apple's Numbers application1, to IntelliJ's IDEA IDE2.
The main improvement between ANTLR4 and ANTLR3 is a change in the parsing algorithm. This new variation of the LL(*) parsing algorithm, coined adaptive LL(*), pushes all of the grammar analysis effort to runtime, making ANTLR able to handle left recursive rules. This new resilience lead to the name "Honey Badger", on which Terence Parr had this to say:
ANTLR v4 is called the honey badger release after the fearless hero of the YouTube sensation, "The Crazy Nastyass Honey Badger". To quote the honey badger, ANTLR v4 just doesn't give a damn. It's pretty bad ass. It'll take just about any grammar you give it at parse correctly. And, without backtracking!*
-- Terence Parr
(To read more, check out the full conversation!)
If you are interested in learning to use ANTLR4, a good place to start would be the official documentation, which provides an excellent introduction to the library itself.
Further Reading:
1 Sourced from a paper written by Terrence Parr himself.
2 Sourced from Jetbrain's official list of third party software in IDEA.
3 On January 24th 2013, the www.antlr.org address was changed from pointing at site for ANTLR version 3 (www.antlr3.org) to ANTLR version 4 (www.antlr4.org). So questions and answers that used www.antlr.org were correct for ANTLR 3.x before this date. The links should be updated to www.antlr3.org for ANTLR 3.x or www.antlr4.org for ANTLR 4.x.
