[Haskell-cafe] Hunting for ghci manual input vs. file input differences again

MarLinn monkleyon at gmail.com
Fri May 5 11:30:34 UTC 2017

> You can use a `Proxy` argument to explicitly signal to GHC what type 
> it should be, or TypeApplications, but I don't think either of those 
> will help with implementing this.

I guess you're right. It seems my examples where only working because 
somewhere along the line types where defaulted to () – throwing away any 
information I did have. I suppose what I would actually need for the 
elusive cast is something like a (forall a . c a :=> d a). I found some 
interesting bits in Data.Constraint.Forall to pursue in that direction, 
but I'm far from understanding how to use them.

Anyway, thanks for the help.

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