[Haskell-cafe] ANNOUNCE: control-monad-failure and safe-failure

Michael Snoyman michael at snoyman.com
Mon Nov 16 14:39:14 EST 2009


We are extremely happy to announce the control-monad-failure and
safe-failure packages for error handling.

control-monad-failure provides a basic notion of failure which does not
commit to any concrete representation.
It is just a version of the MonadError class without the annoying bits.

> class MonadFailure e m where failure :: e -> m a

Instances are provided for several concrete representations of failure
handling: Maybe, Either, ErrorT, Control.Exception.Throw, and [].

safe-failure is a fork of Neil Mitchell's Safe package providing
MonadFailure versions of several partial functions
in the Prelude, which instead of failing with a runtime error fail with

> head :: MonadFailure HeadFailure m => [a] -> m a

This is a joint release from the authors of the attempt and the
control-monad-exception packages,
and accompanying releases of those packages have been made making them adopt
the MonadFailure interface.
We have also created a wiki page explaining our reasons for following this
path in:


Jose Iborra, Nicolas Pouillard and Michael Snoyman
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