[Haskell-cafe] Re: Haskell Zippers on Wikibooks: teasing! :)
Peter Verswyvelen wrote: After my colleague explained me about zippers and how one could derive the datatype using differential rules, I had to read about it. So I started reading http://en.wikibooks.org/wiki/Haskell/Zippers#Mechanical_Differentiation This page contains the sentence: *For a systematic construction, we need to calculate with types. The basics of structural calculations with types are outlined in a separate chapter **Generic Programming*http://en.wikibooks.org/w/index.php?title=Haskell/Generic_Programmingaction=editredlink=1 * and we will heavily rely on this material* * * However, the generic programming link does not exist yet :-) A clear case of laziness on the author's part... wait, that would be me. :-O In any case, contributions to the wikibook would be most welcome. ;-) For now, I'd recommend Generic Programming: An introduction http://www.cse.chalmers.se/~patrikj/poly/afp98/ It's a bit verbose at times, but you only need the first few chapters to get an idea about polynomial functors (sums and pairs) and mu . Regards, apfelmus -- http://apfelmus.nfshost.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: Haskell Zippers on Wikibooks: teasing! :)
On Thu, Jul 16, 2009 at 12:11 PM, Heinrich Apfelmusapfel...@quantentunnel.de wrote: Generic Programming: An introduction http://www.cse.chalmers.se/~patrikj/poly/afp98/ It's a bit verbose at times, but you only need the first few chapters to get an idea about polynomial functors (sums and pairs) and mu . Thanks, that's a really nice introduction, which seems to be at just my level for the moment! :-) D ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Haskell Zippers on Wikibooks: teasing! :)
Matthias Görgens matthias.goerg...@googlemail.com writes: doesn't make much sense to me yet, although I suspect I can read the mu as a lambda on types? Not really. The mu has more to do with recursion. I'd say it's entirely to do with recursion. It's like the Y combinator (or fix) for types, though it is combined with a lambda. mu t . t is like fix (\t - t) -- Jón Fairbairn jon.fairba...@cl.cam.ac.uk http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2009-01-31) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
