[Haskell-cafe] A different Maybe maybe

[Joachim Breitner]

[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 

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Joachim "nomeata" Breitner
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