On Tue, Mar 02, 2010 at 08:20:30PM +0100, Sean Leather wrote:
There are numerous threads on the Haskell Café involving rewriting, refactoring, refining, and in general improving code (for some definition of improve). I am interested in seeing examples of how Haskell code can be rewritten to make it better. Some general examples are:
One handy manual transformation is trying to do more checks on the typechecker. GADT's + phantom types are very useful!
x >>= return . f --> fmap f x or f <$> x -- requires importing Control.Applicative
I think the right-hand side (RHS) is more concise and simpler. The types here do change: the type constructor has a Monad constraint in the left-hand side and a Functor constraint in the RHS. Types that are Monad instances are generally also Functor instances, so this is often possible. I'm convinced the semantics are preserved, though I haven't proven it.
Yes, they are the same, always. -- Felipe.