HaRP

Table of contents:

• What is HaRP?
• History
• Download
• Usage
• Documentation
• ToDo
• Contact Information
• Copyright Announcement

What is HaRP?

HaRP, or Haskell Regular Patterns, is a Haskell extension that extends the normal pattern matching facility with the power of regular expressions. This expressive power is highly useful in a wide range of areas, including text parsing and XML processing. Regular expression patterns in HaRP work over ordinary Haskell lists ([]) of arbitrary type. We have implemented HaRP as a pre-processor to ordinary Haskell.

History

• version 0.2, early Aug 2004:
  • Changed syntax to better match that of the article.
  • Non-greedy patterns is now the default.
  • Added a makefile.
• version 0.1, mid May 2004:
  • First release.

Download

HaRP is distributed along with the haskell-src-exts package, which, incidentally, is needed in order to build the preprocessor.

$> darcs get http://www.cs.chalmers.se/~d00nibro/haskell-src-exts

The package should work on any platform where GHC works. The installation instructions assume a working cabal which means GHC-6.4. For older versions of GHC you'll have to build it yourself (not very difficult).

Usage

Build the packages harp and haskell-src-exts and the preprocessor trhsx.

Use the preprocessor on files containing regular patterns. There are basically two ways to use it:

• Invoke it by hand on Haskell source files. The command is
  trhsx infile [outfile]
  If no outfile is specified, the pre-processor will write the generated output to stdout.
• Use it as a preprocessor for GHC. The command is ghc -F -pgmFtrhsx infile
  The pre-processed files rely on pattern guards and will therefore work with GHC only.

Documentation

This short tutorial should get you started.

There is also a short list of examples of uses of HaRP. If you have a nice, useful example that you would like to share, please contact us and we can put it up with the rest of them.

You can also read our article "Regular Expression Patterns", published in the proceedings of ICFP'04. [ps]

ToDo

• Use a more efficient parser for the matcher backend.
• Enable more extensions (i.e. "normal" extensions) for use with the pre-processor.

Contact us

• Niklas Broberg,
• Andreas Farre,

Copyright Announcement

Please read this copyright note.

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