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Centre for Language Technology

Chalmers University of Technology and University of Gothenburg

What is the BNF Converter?

The BNF Converter is a compiler construction tool generating a compiler front-end from a Labelled BNF grammar. It is currently generating code for the target languages Haskell, Agda, C, C++, C#, Java, and OCaml, as well as XML representations and Pygment syntax highlighters.

Given a Labelled BNF grammar the tool produces:

  • an abstract syntax implementation in the target language,
  • a case skeleton for the abstract syntax in the target language,
  • a pretty-printer in the target language,
  • an Alex, JLex, or Flex lexer generator file ,
  • a Happy, CUP, or Bison parser generator file, and
  • a LaTeX file containing a readable specification of the language.


Install via stack from Stackage:

$ stack install BNFC

Install by Cabal from Hackage:

$ cabal install BNFC

Current development version (source repository on GitHub)

$ git clone


Find the latest releases at

BNFC release 2.9.1 2021-03-01

BNFC release 2.9.0 2020-12-28

BNFC release 2.8.4 2020-10-10

BNFC release 2.8.3 2019-08-27

BNFC release 2.8.2 2018-11-04

BNFC release 2.8.1 2016-10-04

BNFC release 2.8 2015-05-24

BNFC release 2.7.1 2014-10-09

BNFC release 2014-09-26

BNFC release 2014-09-26



Mailing list

Send questions, bug reports, usage news, etc, to our Google group.


Book cover

Implementing Programming Languages, a compiler book using BNFC.

A small example

Content of file
-- A grammar for arithmetical expressions
EAdd. Exp ::= Exp "+" Exp1 ;
ESub. Exp ::= Exp "-" Exp1 ;
EMul. Exp1 ::= Exp1 "*" Exp2 ;
EDiv. Exp1 ::= Exp1 "/" Exp2 ;
EInt. Exp2 ::= Integer ;
coercions Exp 2 ;
Generate a parser (choose your backend):
bnfc --haskell -d   -m  &&  make
bnfc --agda    -d   -m  &&  make
bnfc --c            -m  &&  make
bnfc --cpp          -m  &&  make
bnfc --csharp       -m  &&  make
bnfc --java         -m  &&  make
bnfc --java-antlr   -m  &&  make
bnfc --ocaml        -m  &&  make
bnfc --ocaml-menhir -m  &&  make
Run the test parser, generated e.g. with `--haskell`:
echo "1 + 2 * 3 - 4 / 5" | Calc/Test
BNFC functionality overview: BNFC code generator graph

Large examples

A grammar of C with an example C file.

A grammar of Alfa with an example Alfa file. (For more details, see the Alfa home page.)

A grammar of LBNF. It is at the same time an example LBNF file. The development version of this grammar is used in the implementation of the BNF Converter.

A grammar of Java 1.1 developed by Mike Rainey.


© Andreas Abel, Jonas Almström Duregård, Krasimir Angelov, Jean-Philippe Bernardy, Björn Bringert, Johan Broberg, Kyle Butt, Paul Callaghan, Grégoire Détrez, Markus Forsberg, Ola Frid, Peter Gammie, Thomas Hallgren, Pascal Hof, Simon Huber, Patrik Jansson, Kristofer Johannisson, Antti-Juhani Kaijanaho, Andreas Lööw, Justin Meiners, Kent Mein, Ulf Norell, Gabriele Paganelli, Michael Pellauer, Fabian Ruch, and Aarne Ranta 2002 - 2020.


Free software under the BSD 3-clause license.

Versions until 2.8.4 released under the GNU General Public License (GPL).