[Haskell-cafe] Church Encoding Function

[Jim Apple]

On 3/10/07, Robert Dockins <robdockins at fastmail.fm> wrote:
> I'm pretty sure you can define a catamorphism for any regular algebraic data
> type.  I'm not 100% sure what the story is for non-regular (AKA nested)
> datatypes.

They do exist:

Initial Algebra Semantics is Enough! Patricia Johann and Neil Ghani.
http://crab.rutgers.edu/~pjohann/tlca07.pdf
code:
http://www.cs.nott.ac.uk/~nxg/Tlca07.hs

Jim