Re: [Haskell-cafe] Hello and type-level SKI

Note how the provided code enables a bunch of language extensions, most notably UndecidableInstances. (Yep, that's exactly what it sounds like!) It's quite far removed from standard Haskell or full type inference. On Sep 12, 2014 4:30 PM, "Brandon Allbery" wrote:

On Fri, Sep 12, 2014 at 7:25 PM, Jay Sulzberger wrote:

...

But this is impossible! The type system of Haskell can be handled by a Hindley-Milner-Damas style type checker. Such a type checker always comes to a halt with a Yea or Nay answer. So one cannot get a simulation of the combinators S, K, I inside the Haskell type system.

What have I misunderstood? And, in case GHC really does now handle stuff beyond the HMD horizon, what does the New Core language look like?

Standard Haskell is (or was) H-M extended with typeclasses. GHC moved beyond that years ago; internally it's System Fw ( http://en.wikipedia.org/wiki/System_F#System_F.CF.89), and its Core language reflects this.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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