Hello Luke, Saturday, January 17, 2009, 3:16:06 PM, you wrote:
> fmap id = id > fmap (f . g) = fmap f . fmap g > The first property is how we write "preserving underlying > structure", but this has a precise, well-defined meaning that we can > say a given functor obeys or it does not (and if it does not, we say > that it's a bad instance). But you are correct that Haskell does > not allow us to require proofs of such properties. not haskell itself, but QuickCheck allows. we may even consider lifting these properties to the language level -- Best regards, Bulat mailto:bulat.zigans...@gmail.com _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
