[Haskell-cafe] A different Maybe maybe

Dan Piponi dpiponi at gmail.com
Wed Mar 7 18:43:43 EST 2007


Don't stop at the booleans. Next you can define the natural numbers by

newtype Number = N (forall a.(a->a) -> (a->a))

On 3/7/07, Joachim Breitner <mail at joachim-breitner.de> wrote:

> 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.

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