OK. Again, not sure what going on here. Pattern looks OK to me. Michael ============================= import Control.Monad.Stateimport Data.Map type Prefix = (String,String)type GeneratorState = State ((Map Prefix [String]),Prefix,[String]) non_word = "\n" f key new old = new ++ old buildMap :: GeneratorState (Map Prefix [String])buildMap = do (mp,(pfx1,pfx2),all@(w1:words)) <- get if (Prelude.null all) then {- No more words. Return final map (adding non_word for prefix). -} return (insertWithKey' f (pfx1,pfx2) [non_word] mp) else do {- Add word to map at prefix. Continue. -} put (insertWithKey' f (pfx1,pfx2) [w1] mp, (pfx2,w1), words) buildMap ============================= *Main> :r[1 of 1] Compiling Main ( markov3.hs, interpreted )Ok, modules loaded: Main.*Main> fst $ runState buildMap (singleton ("\n","\n") [], ("\n","\n"), ["I","am","lost."])fromList *** Exception: Pattern match failure in do expression at markov3.hs:13:14-44 --- On Thu, 5/19/11, michael rice <nowgate@yahoo.com> wrote: From: michael rice <nowgate@yahoo.com> Subject: Re: [Haskell-cafe] Trying to return a map from State monad To: "Thedward Blevins" <thedward@barsoom.net> Cc: haskell-cafe@haskell.org Date: Thursday, May 19, 2011, 12:41 PM Ok, I see I left out the "State" word. Should be: type GeneratorState = State (Map Prefix [String],Prefix,[String]) Thanks, Michael --- On Thu, 5/19/11, Thedward Blevins <thedward@barsoom.net> wrote: From: Thedward Blevins <thedward@barsoom.net> Subject: Re: [Haskell-cafe] Trying to return a map from State monad To: "michael rice" <nowgate@yahoo.com> Cc: haskell-cafe@haskell.org Date: Thursday, May 19, 2011, 12:22 PM On Thu, May 19, 2011 at 11:03, michael rice <nowgate@yahoo.com> wrote:
type GeneratorState = (Map Prefix [String],Prefix,[String])
buildMap :: GeneratorState (Map Prefix [String])
You are trying to use a type alias (GeneratorState) as a type constructor. There may be other problems, but that leaps out. -----Inline Attachment Follows----- _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe