[Haskell-beginners] mapKeysMaybe

[Lyndon Maydwell]

Oops disregard that. The mapMaybeWithKey doesn't quite do what I expected.

On Fri, Nov 6, 2015 at 6:43 PM, Lyndon Maydwell <maydwell at gmail.com> wrote:

> Well, this might not be the most efficient, but:
>
> mapKeysMaybe f = Data.Map.mapMaybeWithKey (const . f)
>
>
> What do you reckon?
>
> On Fri, Nov 6, 2015 at 6:29 PM, Dennis Raddle <dennis.raddle at gmail.com>
> wrote:
>
>> Can someone give me a clever way to implement mapKeysMaybe, defined as
>> follows?
>>
>> Ord k => (k -> Maybe k) -> Map k a -> Map k a
>>
>> where the transformed keys that evaluate to Just are the only ones kept?
>>
>> I am thinking this will probably help me understand a new type, like
>> traversable or something.
>>
>>
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>
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