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GNU 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.  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
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, C++ or Java
programming in order to use Bison.

Bison and the parsers it generates are portable, they do not require any
specific compilers.

GNU Bison's home page is

# Installation
## Build from git
Here are basic installation instructions for a repository checkout:

    $ git submodule update --init
    $ ./bootstrap

then proceed with the usual `configure && make` steps.

The file is about building, modifying and checking Bison.

## Build from tarball
See the file INSTALL for generic compilation and installation instructions.

Bison requires GNU m4 1.4.6 or later.  See

## Running a non installed bison
Once you ran `make`, you might want to toy with this fresh bison before
installing it.  In that case, do not use `src/bison`: it would use the
*installed* files (skeletons, etc.), not the local ones.  Use `tests/bison`.

## Colored diagnostics
As an experimental feature, diagnostics are now colored, controlled by the
`--color` and `--style` options.

To use them, install the libtextstyle library before configuring Bison.  It
is available from, for instance

The option --color supports the following arguments:
- always, yes: Enable colors.
- never, no: Disable colors.
- auto, tty (default): Enable colors if the output device is a tty.

To customize the styles, create a CSS file, say `bison-bw.css`, similar to

    /* bison-bw.css */
    .warning   { }
    .error     { font-weight: 800; text-decoration: underline; }
    .note      { }

then invoke bison with `--style=bison-bw.css`, or set the `BISON_STYLE`
environment variable to `bison-bw.css`.

## Relocatability
If you pass `--enable-relocatable` to `configure`, Bison is relocatable.

A relocatable program can be moved or copied to a different location on the
file system.  It can also be used through mount points for network sharing.
It is possible to make symlinks to the installed and moved programs, and
invoke them through the symlink.

See "Enabling Relocatability" in the documentation.

## Internationalization
Bison supports two catalogs: one for Bison itself (i.e., for the
maintainer-side parser generation), and one for the generated parsers (i.e.,
for the user-side parser execution).  The requirements between both differ:
bison needs ngettext, the generated parsers do not.  To simplify the build
system, neither are installed if ngettext is not supported, even if
generated parsers could have been localized.  See for more

# Questions
See the section FAQ in the documentation (doc/ for frequently
asked questions.  The documentation is also available in PDF and HTML,
provided you have a recent version of Texinfo installed: run `make pdf` or
`make html`.

If you have questions about using Bison and the documentation does not
answer them, please send mail to <>.

# Bug reports
Please send bug reports to <>.  Be sure to include the
version number from `bison --version`, and a complete, self-contained test
case in each bug report.

# Copyright statements
For any copyright year range specified as YYYY-ZZZZ in this package, note
that the range specifies every single year in that closed interval.


Copyright (C) 1992, 1998-1999, 2003-2005, 2008-2015, 2018-2020 Free
Software Foundation, Inc.

This file is part of GNU bison, the GNU Compiler Compiler.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the "GNU Free
Documentation License" file as part of this distribution.

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