[Haskell] ANN: Catch (first ever release)

Neil Mitchell ndmitchell at gmail.com
Fri Jun 8 09:01:48 EDT 2007


Do you sometimes encounter the dreaded "pattern match failure: head
[]" message? Do you have incomplete patterns which sometimes fail? Do
you have incomplete patterns which you know don't fail, but still get
compiler warnings about them? Would you like to statically ensure the
absence of all calls to error?

For the last few years I've been working on a pattern-match checker
for Haskell, named Catch. I'm now happy to make a release:

Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/catch-0.1
Homepage: http://www-users.cs.york.ac.uk/~ndm/catch/
User manual: http://www.cs.york.ac.uk/fp/darcs/catch/catch.htm

While a darcs version is available, I strongly recommend the use of
the tarball on hackage.


* Detects all incomplete patterns and calls to error
* Full support for Haskell, through the use of Yhc as a front end
* Automatic - no annotations are required
* Fast - checking times of under 5 seconds (excluding Yhc compilation)
are typical


* Requires Yhc to be installed, which doesn't accept most Haskell
extensions. This will be fixed once GHC.Core is available as a
standalone library. The underlying tool is not limited to Haskell 98
in any way.

Success stories:

* The darcs version of HsColour has been proven free of pattern match
errors, and Catch was able to find three previously unknown crashes
which could be triggered by a malformed document.
* System.FilePath has been checked, and is free of pattern-match errors
* XMonad's central StackSet.hs module has been checked repeatedly, as
it has evolved. Unfortunately currently this module goes beyond
Haskell 98, but this should be fixed shortly.

If you have any experiences with Catch, I'd be very interested to hear them.



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