[Haskell-cafe] Couple of formal questions

Wouter Swierstra wss at cs.nott.ac.uk
Thu May 1 10:54:43 EDT 2008

Hi Creighton,

> Where could I find a good treatment on data vs. codata & the  
> difference between well-founded recursion & well-founded(?)  
> corecursion?

Bart Jacobs has some good papers on the subject. I found the draft of  
his book "Introduction to Coalgebra" quite good:


> Where could I find a proof that the initial algebras & final  
> coalgebras of CPO coincide?  I saw this referenced in the  
> "Bananas.." paper as a fact, but am not sure where this comes from.

I couldn't find the statement you are referring to in "Functional  
Programming with Bananas, Lenses, Envelopes, and Barbed Wire" - but  
I'm not sure if this holds for every CPO. Having data and codata  
coincide is quite a curious property (I think it's sometimes called  
"algebraic compactness" - but don't quote me on this).

Hope this helps,


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