[Haskell-cafe] A different Maybe maybe

[Lennart Augustsson]

Hey, welcome to to the group who have reinvented Church encoding of  
data types. :)

	-- Lennart

On Mar 7, 2007, at 22:32 , Joachim Breitner wrote:

> [Also on http://www.joachim-breitner.de/blog/archives/229-A- 
> different-Maybe-maybe.html]
>
> Hi,
>
> For a while I have been thinking: Isn’t there a way to get rid of the
> intermediate Maybe construct in a common expression like “fromMaybe
> default . lookup”. It seems that a way to do that would be to pass  
> more
> information to the Maybe-generating function: What to do with a
> Just-Value, and what to return in case of Nothing. This leads to a new
> definion of the Maybe data type as a function. Later I discovered that
> this seems to work for any algebraic data type.
>
> This is probably nothing new, but was offline at the time of  
> writing, so
> I didn’t check. This means that this might also be total rubbish.  
> Enjoy.
>
>       * “Algebraic Data Type Done Differently” (PDF-File) at
>         http://www.joachim-breitner.de/various/FunctionalMaybe.pdf
>       * “Algebraic Data Type Done Differently” (Literate Haskell  
> Source)
>         at http://www.joachim-breitner.de/various/FunctionalMaybe.lhs
>
> Comments are appreciated.
>
> Greetings from my holidays,
> Joachim
>
> -- 
> Joachim "nomeata" Breitner
>   mail: mail at joachim-breitner.de | ICQ# 74513189 | GPG-Key: 4743206C
>   JID: joachimbreitner at amessage.de | http://www.joachim-breitner.de/
>   Debian Developer: nomeata at debian.org
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