# Alex: A Lexical Analyser Generator
[](http://travis-ci.org/simonmar/alex)
Alex is a Lex-like tool for generating Haskell scanners. For complete
documentation, see the doc directory.
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Alex version 2.0 has changed fairly considerably since version 1.x,
and the syntax is almost completely different. For a detailed list of
changes, see the release notes in the documentation.
Alex is now covered by a BSD-Style licence; see the licence file in
the 'doc' directory for details.
The sources are in the 'src' directory and the documentation in the 'doc'
directory; various examples are in the 'examples' subdirectory.
The source code in the 'src' and 'examples' directories is intended
for a Haskell 98 compiler with hierarchical modules. It should work
with GHC >= 5.04.
## Build Instructions
If you just want to *use* Alex, you can download or install (via
`cabal install alex`) an
[Alex release from Hackage](https://hackage.haskell.org/package/alex); also note that
distributions such as the
[Haskell Platform](https://www.haskell.org/platform/) and other package
manager-based distributions provide packages for Alex. Moreover,
recent versions of `cabal` will automatically install the required
version of `alex` based on
[`build-tools`/`build-tool-depends` declarations](http://cabal.readthedocs.io/en/latest/developing-packages.html#pkg-field-build-tool-depends).
Read on if you want to build Alex directly from Git.
Alex is built using GHC & Cabal; so first install
[GHC](https://www.haskell.org/ghc) and
[`cabal-install-2.0`](https://www.haskell.org/cabal) (or later).
Since Alex itself is implemented in terms of an Alex scanner,
bootstrapping Alex is a bit tricky:
You need to have the build-tools `alex` and `happy` manually
installed; either via your system package manager distribution, the
Haskell Platform, or e.g. via (run this outside the Git repository!):
$ cabal install alex happy
which installs them into `${HOME}/.cabal/bin` by default (make sure
they're in your `$PATH` for the next steps!).
### Variant A
First you need to generate the pre-processed templates via
$ cabal new-run gen-alex-sdist
(otherwise `cabal install` will complain about
"`data/AlexTemplate: copyFile: does not exist (No such file or directory)`")
And then you can install `alex` simply by invoking
$ cabal install
from inside the Git folder.
### Variant B
Alternatively, you can use the `Makefile` which automates the steps of
producing a self-contained pre-bootstrapped source distribution with
pre-generated lexer/scanners (and which also performs the `cabal
new-run gen-alex-sdist` pre-preprocessing step):
$ make sdist
$ cabal install dist/alex-*.tar.gz
For convenience, there's also a `make sdist-test` target which builds the
source source tarball and runs the test-suite from within the source dist.
## Contributing & Reporting Issues
Please report any bugs or comments at https://github.com/simonmar/alex/issues
Share and enjoy,
Chris Dornan: cdornan@arm.com
Isaac Jones: ijones@syntaxpolice.org
Simon Marlow: simonmar@microsoft.com