# Lambda over types.

**Keith Wansbrough
**
Keith.Wansbrough@cl.cam.ac.uk

*Fri, 22 Mar 2002 09:34:08 +0000*

anatoli <anatoli@yahoo.com> writes:
>* ghc -fglasgow-exts -fallow-undecidable-instances allows =
*
>* constructs which amount to lambda abstraction over types. =
*
>* I've written a small untyped lambda calculus interpreter =
*
>* in the Haskell class/instance sublanguage, just to prove
*>* this point. (The terms are Haskell *types*.)
*
Cool!
Some time ago I wrote a Turing machine evaluator in Haskell types with un=
decidable instances. It's described at
http://www.chttp://www.cl.cam.ac.uk/~kw217/research/misc/undec.html
Enjoy!
--KW 8-)
-- =
Keith Wansbrough <kw217@cl.cam.ac.uk>
http://www.cl.cam.ac.uk/users/kw217/
University of Cambridge Computer Laboratory.