Hi, It seems that I need to distinguish between a theory for Haskell and a given implementation (GHCi). I have two further queries based on the replies; 1)
Obviously I get two different types Wrong. You get exactly the same type, it's just that GHCi detected that you have a fancy name for this type, so it gives you that name. It's not type system, it's just GHCi.
Are you saying there is just one type? (not two isomorphic types because there is only one of them with two names) 2)
In the case of the function Haskells type system seems to pick up enough
information to determine that “ww” is a Name.
Nope. "ww" is still a [Char] for the compiler. And you do not even check for the type of "ww".
:t snd . (\x -> (getName x, x)) $ "ww" ... :: String
Why are the GHCi commands :t "ww" and :t getName("ww") not a valid type checks? Pat pbrowne wrote:
Hi, I am studying the underlying semantics behind Haskell and to what degree those semantics are actually implemented. I need to clarify what a *type synonym* actual means in relation to Haskell's logic (or formal semantics). I used the following type synonym: