On Wed, Apr 04, 2007 at 11:15:25PM +0200, Stefan Holdermans wrote: > Edsko, > > >>James H. Morris. Lambda calculus models of programming languages. > >>Technical Report MIT-LCS//MIT/LCS/TR-57, Massachusetts Institute of > >>Technology, 1968. > > > >Aah, I guess that's a bit old to be avaiable online :) Does he talk > >about negative datatypes though? The Y combinator itself isn't really > >the point of my little exercise; it's more that I can code the Y > >combinator without making any recursive calls (in fact, there > >aren't any > >recursive calls in that program at all). > > If I recall correctly that's exactly what he demonstrates, i.e., that > fixed-point combinators can be encoded without value-level recursion, > but by instead making use of types that are contravariantly recursive.
I see. Thanks for the reference! Must try to dig that up (the MIT publication database appears to be offline at the moment). Thanks again, Edsko _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe