[Haskell-cafe] Hello and type-level SKI

Tikhon Jelvis tikhon at jelv.is
Fri Sep 12 23:46:20 UTC 2014


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" <allbery.b at gmail.com> wrote:

> On Fri, Sep 12, 2014 at 7:25 PM, Jay Sulzberger <jays at panix.com> 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 at gmail.com
> ballbery at sinenomine.net
> unix, openafs, kerberos, infrastructure, xmonad
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>
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