6 Nov
2015
6 Nov
'15
2:43 a.m.
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
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.
_______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners