From [1]:
-- | Fail with a message. This operation is not part of the -- mathematical definition of a monad, but is invoked on pattern-match -- failure in a @do@ expression. -- -- As part of the MonadFail proposal (MFP), this function is moved -- to its own class 'MonadFail' (see "Control.Monad.Fail" for more -- details). The definition here will be removed in a future -- release. fail :: String -> m a fail s = errorWithoutStackTrace s Best regards, Manuel (also a newbie) [1] http://hackage.haskell.org/package/base-4.9.1.0/docs/src/GHC.Base.html#Monad
thanks and what is the purpose of
fail _ = nothing
Cheers
Fred _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners