[Haskell-cafe] Re: [Haskell] pros and cons of static typing andside effects ?

[Ralf Lammel]

Technically this is trivial it seems. I think that some people consider this proposal a problem because typos (misspelled type parameters) immediately lead to the accidental exploration of a more advanced type-system feature and correspondingly more involved error messages. Of course, the type checker could perhaps consider adding "Did you really mean to ...?".

Ralf

> I once read a paper about type classes and existentials (can't remember
> exact title or author, was it Läufer?) where the proposal was to make
> existential quantification implicit (just as the universal one is in
> Haskell98). That is, any type variable that appears on the rhs of a
> data type, but not on the lhs, is implicitly existentially quantified,
> as in
> 
>   data XWrap = Show a => XWrap a
> 
> I always thought this was a pretty nice idea.