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Bison - GNU parser generator

Introduction to Bison

Bison is a general-purpose parser generator that converts an annotated context-free grammar into a deterministic LR or generalized LR (GLR) parser employing LALR(1) parser tables. As an experimental feature, Bison can also generate IELR(1) or canonical LR(1) parser tables. Once you are proficient with Bison, you can use it to develop a wide range of language parsers, from those used in simple desk calculators to complex programming languages.

Bison is upward compatible with Yacc: all properly-written Yacc grammars ought to work with Bison with no change. Anyone familiar with Yacc should be able to use Bison with little trouble. You need to be fluent in C or C++ programming in order to use Bison. Java is also supported as an experimental feature.

Downloading Bison

Bison can be found on [via http] and [via FTP]. It can also be found on one of our FTP mirrors. To verify the files, you may want to import Bison's GPG keyring.

Test versions of Bison can be found on [via FTP]. The latest bleeding-edge version of the source code, along with a revision history, can be found in the Bison Savannah repository. Please note that we do not suggest using Bison sources from these locations for production use.


A manual is available in several formats. You may also find more information about Bison by looking at your local documentation. For example, you might try info bison or man bison at the shell prompt.

Mailing Lists

To subscribe to any GNU mailing list, please send an empty mail with a Subject: header line of just "subscribe" to the relevant -request list. For example, to subscribe yourself to the main list, you would send mail to <> with no body and a Subject: header line of just "subscribe".

The main discussion list for new users is <>, and is used to discuss all aspects of Bison, including development and porting. Announcements about Bison and most other GNU Software are also made on <>.

Please send patches to the source code, to improve or fix bugs in Bison, to the <> list. We prefer patches against the latest Savannah sources.

Request an Enhancement

If you would like any new feature to be included in future versions of Bison, please send a request to <>.

Please remember that development of Bison is a volunteer effort, and you can also contribute to its development. For information about contributing to the GNU Project, please read How to help GNU.

Report a Bug

If you think you have found a bug in Bison, then you should send as complete a report as possible to <>. Problems about translations should be reported to


Bison is currently being maintained by Akim Demaille, Joel E. Denny, and Paul Eggert.

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