Am Donnerstag, 24. November 2005 02:08 schrieb David Menendez: > Wolfgang Jeltsch writes: > > If we use an implementation of State *without lazy patterns*, it > > becomes something like this: > > > > \s -> case next s of > > (x,s') -> case everyting s' of > > (xs,s'') -> ((x : xs),s'') > > > > Note that I used case expressions to realize strict patterns because > > pattern binding in let expressions is implicitely lazy. > > > > Now lets apply the function denoted by the last code fragment to some > > initial state and try to extract just the first element of the > > output. In order to do so we have to take the result of the function > > and match it against ((x : _),_). Especially, we have to reduce the > > pair, i.e., we have to make sure that it's really an application of > > (,) and not _|_. > > Would the lazy pattern match be equivalent to using fst and snd? > > \s -> case next s of > p1 -> case everything (snd p1) of > p2 -> (fst p1 : fst p2, snd p2)
I think so. Best wishes, Wolfgang _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
