[Haskell-cafe] Maybe, maybe not.

michael rice nowgate at yahoo.com
Tue Jan 26 23:12:56 EST 2010

Didn't recognize the sameness. Aside from there being many ways to do the same thing, partial application makes the mixup even merrier.



--- On Tue, 1/26/10, Edward Z. Yang <ezyang at MIT.EDU> wrote:

From: Edward Z. Yang <ezyang at MIT.EDU>
Subject: Re: [Haskell-cafe] Maybe, maybe not.
To: "michael rice" <nowgate at yahoo.com>
Cc: "haskell-cafe" <haskell-cafe at haskell.org>
Date: Tuesday, January 26, 2010, 10:52 PM

Excerpts from michael rice's message of Tue Jan 26 21:34:42 -0500 2010:
> fromMaybe d x = case x of {Nothing -> d;Just v  -> v}
> fromMaybe z = maybe z id

They're equivalent.  Here the definition of maybe:

    maybe :: b -> (a -> b) -> Maybe a -> b
    maybe n _ Nothing  = n
    maybe _ f (Just x) = f x


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