Re: [Haskell-cafe] Manual type-checking in graphs: Avoidable?

Yes, that is my point. Existentials cannot be unwrapped. On Sat, Feb 20, 2016 at 4:18 AM, Kosyrev Serge <_deepfire@feelingofgreen.ru> wrote:

Jeffrey Brown writes:

...

After further study I believe existentials are not (at least alone) enough to solve the problem. .. getInt :: ShowBox -> Int getInt (SB i) = i

will not compile, because it cannot infer that i is an Int:

You take a value of an existentially quantified type (which means it can be anything at all, absent some extra context) and *proclaim* it is an integer.

On what grounds should the compiler accept your optimistic restriction?

-- с уважениeм / respectfully, Косырев Сергей

-- Jeffrey Benjamin Brown