alex
Alex is a tool for generating lexical analysers in Haskell
Version on this page: | 3.2.7.1 |
LTS Haskell 23.0: | 3.5.1.0 |
Stackage Nightly 2024-12-12: | 3.5.1.0 |
Latest on Hackage: | 3.5.1.0 |
alex-3.2.7.1@sha256:ab26a38cefae59403f746370e5a0c943b8d5bda098eb83f37052b2429ee780ce,3911
Module documentation for 3.2.7.1
There are no documented modules for this package.
Alex: A Lexical Analyser Generator
Alex is a Lex-like tool for generating Haskell scanners. For complete documentation, see the doc directory.
Alex is 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 to work
with GHC >= 7.0.
Build Instructions
If you just want to use Alex, you can download or install (via
cabal install alex
) an
Alex release from Hackage; also note that
distributions such as the
Haskell 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.
Read on if you want to build Alex directly from Git.
Alex is built using GHC & Cabal; so first install
GHC and
cabal-install-2.0
(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 are in your $PATH
for the next steps!).
Variant A
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:
$ make sdist
$ cabal install dist/alex-*.tar.gz
For convenience, there is 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: [email protected]
Isaac Jones: [email protected]
Simon Marlow: [email protected]
and recent contributors.
Current Maintainers
-
John Ericson (@Ericson2314)
-
Simon Marlow (@simonmar)
Changes
Change in 3.2.7.1
- Fix bug with repeated numeral characters outside of
r{n,m}
repetitions. This was a regression introduced in 3.2.7.
Changes in 3.2.7
-
Allow arbitrary repetitions in regexps. Previously, the
r{n,m}
and related forms were restricted to single digit numbersn
andm
. -
DFA minimization used to crash on tokens of the form
c*
which produce automata with only accepting states. Considering the empty set of non-accepting states as an equivalence class caused minimization to crash with exception. -
The
small_base
flag is removed. Extremely old GHCs will no longer build. -
A number of bug fixes and clearer diagnostics.
Changes in 3.2.6:
-
Support for the GHC 9.2.
The array access primops now use the fixed-sized numeric types corresponding to the width of the data accessed. Additionally, the primops to convert to and from fixed-sized numeric types have been given new names.
9.2 isn’t cut yet, so these changes are somewhat speculative. Unfortunately, GHC must used a released version of Alex (and Happy) at all times until further changes have been made, so we must make the release to actually implement these changes in GHC.
If the final GHC 9.2 ends up being different, this release will be marked broken to make it less likely people use it by accident.
Changes in 3.2.5:
- Build fixes for GHC 8.8.x
Changes in 3.2.4:
- Remove dependency on QuickCheck
- Change the way that bootstrapping is done: see README.md for build instructions
Changes in 3.2.3:
- fix issue when using cpphs (#116)
Changes in 3.2.2:
- Manage line length in generated files [GH-84]
- Fix issue when identifier with multiple single quotes, e.g.
foo''
was used - Allow omitting spaces around
=
in macro definitions - Include pre-generated Parser.hs and Scan.hs in the Hackage upload, to make bootstrapping easier.
Changes in 3.2.1:
- Fix build problem with GHC; add new test tokens_scan_user.x
Changes in 3.2.0:
- Allow the token type and productions to be overloaded, and add new directives: %token, %typeclass, %action. See “Type Signatures and Typeclasses” in the manual.
- Some small space leak fixes
Changes in 3.1.7:
- Add support for
%encoding
directive (allows to control--latin1
from inside Alex scripts) - Make code forward-compatible with in-progress proposals
- Suppress more warnings
Changes in 3.1.6:
sdist
for 3.1.5 was mis-generated, causing it to ask for Happy when building.
Changes in 3.1.5:
- Generate less warning-laden code, and suppress other warnings.
- Bug fixes.
Changes in 3.1.4:
- Add Applicative/Functor instances for GHC 7.10
Changes in 3.1.3:
- Fix for clang (XCode 5)
Changes in 3.1.2:
- Add missing file to extra-source-files
Changes in 3.1.1:
- Bug fixes (#24, #30, #31, #32)
Changes in 3.1.0:
- necessary changes to work with GHC 7.8.1
Changes in 3.0 (since 2.3.5)
-
Unicode support (contributed mostly by Jean-Philippe Bernardy, with help from Alan Zimmerman).
-
An Alex lexer now takes a UTF-8 encoded byte sequence as input (see Section 5.1, “Unicode and UTF-8”. If you are using the “basic” wrapper or one of the other wrappers that takes a Haskell String as input, the string is automatically encoded into UTF-8 by Alex. If your input is a ByteString, you are responsible for ensuring that the input is UTF-8 encoded. The old 8-bit behaviour is still available via the –latin1 option.
-
Alex source files are assumed to be in UTF-8, like Haskell source files. The lexer specification can use Unicode characters and ranges.
-
alexGetChar
is renamed toalexGetByte
in the generated code. -
There is a new option,
--latin1
, that restores the old behaviour.
-
-
Alex now does DFA minimization, which helps to reduce the size of the generated tables, especially for lexers that use Unicode.