I understand why you want to do this, but unfortunately, it may be only an illusion that Haskell classes seem to be “open” in the way that you say. Many people feel that the possibility of doing this is a bug in the Haskell specification, for reasons I’ll explain below. Anyway, if it is really … Read more
This is because String is just a type alias for [Char], which is just the application of the type constructor [] on the type Char, so this would be of the form ([] Char). which is not of the form (T a1 .. an) because Char is not a type variable. The reason for this … Read more
These links may be helpful: Evaluating cellular automata is comonadic. In particular, “whenever you see large datastructures pieced together from lots of small but similar computations there’s a good chance that we’re dealing with a comonad”. Sequences, streams, and segments Comonads in everyday life
The short answer is, magic :-). This is to say that automatic deriving is baked into the Haskell spec, and every compiler can choose to implement it in its own way. There’s lots of work on how to make it extensible however. Derive is a tool for Haskell to let you write your own deriving … Read more
I would say that an interface is kind of like a type class SomeInterface t where all of the values have the type t -> whatever (where whatever does not contain t). This is because with the kind of inheritance relationship in Java and similar languages, the method called depends on the type of object … Read more