haskell: > Hello, > > I was just doing Exercise 7.1 of Hal Daum?'s very good "Yet Another > Haskell Tutorial". It consists of 5 short functions which are to be > converted into point-free style (if possible). > > It's insightful and after some thinking I've been able to come up with > solutions that make me understand things better. > > But I'm having problems with one of the functions: > > func3 f l = l ++ map f l > > Looks pretty clear and simple. However, I can't come up with a solution. > Is it even possible to remove one of the variables, f or l? If so, how?
The solution is to install lambdabot ;) Point free refactoring: lambdabot> pl func3 f l = l ++ map f l func3 = ap (++) . map Find the type: lambdabot> type ap (++) . map forall b. (b -> b) -> [b] -> [b] Get some free theorems: lambdabot> free f :: (b -> b) -> [b] -> [b] f . g = h . f => map f . f g = f h . map f :) -- Don _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe