[Haskell-cafe] Does this function have a name?

Paul Brauner polux2001 at gmail.com
Fri Apr 7 08:57:23 UTC 2017

Oops, there's a free variable in there, let me fix it:

first f [] = Nothing
first f (x:xs) = fmap (:xs) (f x) <|> fmap (x:) (first f xs)


On Fri, Apr 7, 2017 at 10:42 AM Paul Brauner <polux2001 at gmail.com> wrote:

> Hello Haskell Cafe,
> I had to write the following function and I was wondering if it (or its
> generalization to Alternative or Traversable) was exposed by some library
> under a different name:
> first [] = Nothing
> first (t:ts) = fmap (:ts) (s t) <|> fmap (t:) (first ts)
> Somehow it is to "traverse" as "any" is to "all".
> Cheers,
> Paul
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