* Niklas Hambüchen <m...@nh2.me> [2013-03-16 03:49:29+0000] > I would agree that what attoparsec does for <|> of Alternative and mplus > for MonadPlus is correct since e.g. the mplus laws say that a failure > must be identity and therefore the following alternatives must be > considered. I also find it very convenient that attoparsec works this > way, and prefer it to what parsec does by default.
empty/mzero are indeed identities in Parsec. What doesn't hold is the law v >> mzero = mzero But this one is often violated: > flip runState 0 $ runMaybeT mzero (Nothing,0) > flip runState 0 $ runMaybeT $ lift (modify (+1)) >> mzero (Nothing,1) Roman _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
