|Original author(s)||Terence Parr and others|
|Initial release||February 1992|
|Stable release||4.2 / 3.5.1 / February 3, 2014/ January 4, 2014|
|Development status||in active development|
In computer-based language recognition, ANTLR (pronounced Antler), or ANother Tool for Language Recognition, is a parser generator that uses LL(*) parsing. ANTLR is the successor to the Purdue Compiler Construction Tool Set (PCCTS), first developed in 1989, and is under active development. Its maintainer is professor Terence Parr of the University of San Francisco.
ANTLR allows generating lexers, parsers, tree parsers, and combined lexer-parsers. Parsers can automatically generate abstract syntax trees which can be further processed with tree parsers. ANTLR provides a single consistent notation for specifying lexers, parsers, and tree parsers. This is in contrast with other parser/lexer generators and adds greatly to the tool's ease of use.
By default, ANTLR reads a grammar and generates a recognizer for the language defined by the grammar (i.e. a program that reads an input stream and generates an error if the input stream does not conform to the syntax specified by the grammar). If there are no syntax errors, then the default action is to simply exit without printing any message. In order to do something useful with the language, actions can be attached to grammar elements in the grammar. These actions are written in the programming language in which the recognizer is being generated. When the recognizer is being generated, the actions are embedded in the source code of the recognizer at the appropriate points. Actions can be used to build and check symbol tables and to emit instructions in a target language, in the case of a compiler.
As well as lexers and parsers, ANTLR can be used to generate tree parsers. These are recognizers that process abstract syntax trees which can be automatically generated by parsers. These tree parsers are unique to ANTLR and greatly simplify the processing of abstract syntax trees.
While ANTLR itself is free, the documentation necessary to use it is not. The ANTLR manual is a commercial book, The Definitive ANTLR Reference. Free documentation is limited to a handful of tutorials, code examples, and very basic API listings.
Several plugins have been developed for the Eclipse development environment to support the ANTLR grammar. There is ANTLR Studio, a proprietary product, as well as the ANTLR 2 and 3 plugins for Eclipse hosted on SourceForge.
ANTLR v4 deals with left recursion correctly (except for indirect left recursion, i.e. grammars rules x which refer to y which refer to x) and supports actions and attributes flexibly. That is, actions can be defined separately from the grammar, allowing for easier targeting of multiple languages.
ANTLR is a parser generator that can be used to read, process, execute, or translate structured text or binary files. It’s used in academia and industry to build all sorts of languages, tools, and frameworks. Twitter search uses ANTLR for query parsing, with over 2 billion queries a day. The languages for Hive and Pig, the data warehouse and analysis systems for Hadoop, both use ANTLR. Lex Machina uses ANTLR for information extraction from legal texts. Oracle uses ANTLR within SQL Developer IDE and their migration tools. NetBeans IDE parses C++ with ANTLR. The HQL language in the Hibernate object-relational mapping framework is built with ANTLR.
Potential uses are: configuration file readers, legacy code converters, wiki markup renderers, JSON parsers, object-relational database mappings, describing 3D visualizations, injecting profiling code into Java source code.
Where is it used?
Here is a non-comprehensive list of software built using ANTLR:
- OpenJDK Compiler Grammar project experimental version of the javac compiler based upon a grammar written in ANTLR.
- Apex, Salesforce.com's programming language.
- The expression evaluator in Numbers, Apple's spreadsheet.
- Twitter's search query language.
- Weblogic server
- SML/NJ Language Processing Tools: User Guide
- Parr, Terence (May 17, 2007), The Definitive Antlr Reference: Building Domain-Specific Languages (1st ed.), Pragmatic Bookshelf, p. 376, ISBN 0-9787392-5-6
- Parr, Terence (December 2009), Language Implementation Patterns: Create Your Own Domain-Specific and General Programming Languages (1st ed.), Pragmatic Bookshelf, p. 374, ISBN 978-1-934356-45-6
- Parr, Terence (January 15, 2013), The Definitive ANTLR 4 Reference (1st ed.), Pragmatic Bookshelf, p. 328, ISBN 978-1-93435-699-9
- T. J. Parr, R. W. Quong, ANTLR: A Predicated-LL(k) Parser Generator, Software—Practice and Experience, Vol. 25(7), 789–810 (July 1995)