[Haskell-cafe] Existential quantification of environments.

[Wolfgang Jeltsch]

Am Dienstag, 22. November 2005 17:19 schrieben Sie:
> Wolfgang Jeltsch wrote:
> >>This seems to suggest:
> >>
> >>    Add a == exists (add :: a -> a -> a)
> >
> >Doesn't "exists" normally quantify over types and not over values?
>
> It is quantifying over types, it is saying there exists a type "a -> a -> a"
> that has at least one value we will call "add"...

It says that there exists a value add.  With quantifying over types I meant 
something like this:

	exists a. <some type using the type variable a>

This is how forall in GHC and Hugs looks like.

> [...]

Best wishes,
Wolfgang