So are you suggesting that we add these to Data.Foldable?
headMay = foldr (\x _ -> Just x) Nothing
lastMay = foldl (\_ x -> Just x) Nothing
On Feb 26, 2015 9:18 AM, "Petr Pudlák"
Hi,
today I was a bit surprised that apparently there is no easy way how to safely get the head element of `Seq` in a point-free way. Of course there is `viewl`, but it seems the data type has no folding function (something like 'foldViewL :: b -> (a -> Seq a -> b) -> b`.
Is there any existing function like `Seq a -> Maybe a` to safely retrieve the head (or last) element?
If not, I'd suggest to add
headMaybe :: (Foldable t) => t a -> Maybe a headMaybe = getFirst . foldMap (First . Just)
and similarly lastMaybe to Data.Foldable.
Thanks, Petr
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