On Mon, Apr 16, 2012 at 6:57 PM, Nicolas Frisby <[email protected]>wrote:
> I'm simulating skolem variables in order to fake universal > quantification in constraints via unsafeCoerce. > > http://hpaste.org/67121 > > I'm not familiar with various categories of types from the run-time's > perspective, but I'd be surprised if there were NOT a way to use this > code to create run-time errors. > > Is there a way to make it safer? Perhaps by making Skolem act more > like GHC's Any type? Or perhaps like the -> type? I'd like to learn > about the varieties of types from the run-time's perspective. > FWIW- I have a version of this concept packaged up in the constraints package. I had a small example that abused flexible instances and MPTCs to cause the single Skolem version of my code to fail. However, when I refined it to use two Skolem variables I wasn't able to derive sufficient Oleggery to break it. That said, an absence of a counter-example isn't a proof that it can't exist. http://hackage.haskell.org/packages/archive/constraints/0.3/doc/html/src/Data-Constraint-Forall.html
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