Folks, 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 Failure.
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: http://www.haskellwiki.org/Failure Thanks, Jose Iborra, Nicolas Pouillard and Michael Snoyman