Alex is a tool for generating lexical analysers in Haskell. It takes a description of tokens based on regular expressions and generates a Haskell module containing code for scanning text efficiently. It is similar to the tool lex or flex for C/C++.
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.