Alex: A Lexical Analyser Generator
Alex is a Lex-like tool for generating Haskell scanners. For complete documentation, see the doc directory.
Alex is built using Cabal. First install GHC and cabal-install, then:
$ cabal configure $ cabal build $ cabal install
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.
Please report any bugs or comments at https://github.com/simonmar/alex/issues
Share and enjoy,
Chris Dornan: email@example.com
Isaac Jones: firstname.lastname@example.org
Simon Marlow: email@example.com
Changes in 3.2.1:
Fix build problem with GHC; add new test tokensscanuser.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
%encodingdirective (allows to control
--latin1from inside Alex scripts)
- Make code forward-compatible with in-progress proposals
- Suppress more warnings
Changes in 3.1.6:
sdistfor 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.
alexGetCharis renamed to
alexGetBytein 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.