AW: [Haskell-cafe] Fixed-Point Combinators

[Holger Siegel]

--- Adrian Neumann <aneumann at inf.fu-berlin.de> schrieb am Mi, 16.7.2008:

> Von: Adrian Neumann <aneumann at inf.fu-berlin.de>
> Betreff: [Haskell-cafe] Fixed-Point Combinators
> An: "Haskell Cafe mailing list" <haskell-cafe at haskell.org>
> Datum: Mittwoch, 16. Juli 2008, 21:17
> Hello,
> 
> while studying for a exam I came across this little pearl:
> 
> Y = (L L L L L L L L L L L L L L L L L L L L L L L L L L L
> L)
> where
> L = λabcdefghijklmnopqstuvwxyzr. (r (t h i s i s a f i x e
> d p o i n  
> t c o m b i n a t o r))
> 
> posted by Cale Gibbard to this list. Now I'm wondering
> how exactly  
> does one finde such awesome λ expressions? Is there some
> mathemagical  
> background that lets one conjure such beasts?

Have a look at http://citeseer.ist.psu.edu/251224.html

In this paper Jeroen Fokker describes how to derive a one-combinator basis from the SKI combinators in a systematic way. Maybe it can give you some hints how to treat this kind of problem.




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