[Haskell-cafe] Missing common function for Maybe types

[Vanessa McHale]

That doesn't exactly make sense. You'd need two versions of that
function in all likelihood - one left-biased and another right-biased.


On 07/31/2018 02:07 AM, Marc Busqué wrote:
> Hi!
>
> I have two functions:
>
> ```
> foo :: a -> Maybe b
> bar :: a -> Maybe c
> ```
>
> From which I want to build a higher order function:
>
> ```
> foobar :: a -> (a -> Maybe b) -> (a -> Maybe c) -> Either b c
> ```
>
> The implementation I need is:
>
> ```
> foobar x f g =
>   case (f x) of
>     Nothing -> g x
>     Just y  -> Just y
> ```
>
> I'm a bit surprised that looking at hoogle I don't find a built-in
> solution for this quite common need for `Maybe` types (or perhaps for
> any monad).
>
> Am I looking in the wrong way? Does it exist a similar abstraction but
> with a different shape?
>
> Thanks in advance,
>
> Marc Busqué
> http://waiting-for-dev.github.io/about/
>
>
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-- 



*Vanessa McHale*
Functional Compiler Engineer | Chicago, IL

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