concat1 and concatMap1

[Icelandjack]

Like #49 but I don't want to clutter.

I needed concatMap1 just now. Would people be against adding

concat1 :: Foldable1 f => f (NonEmpty a) -> NonEmpty a
concat1 = concatMap1 id

concatMap1 :: forall f a b. Foldable1 f => (a -> NonEmpty b) -> (f a -> NonEmpty b)
concatMap1 f = foldr1m h where

  h :: a -> Maybe (NonEmpty b) -> NonEmpty b
  h a Nothing  = f a
  h a (Just x) = f a <> x

Similar functions exist as comments in Data.Semigroup.Foldable:

concat1    :: Foldable1 t => t (Stream a) -> Stream a
concatMap1 :: Foldable1 t => (a -> Stream b) -> t a -> Stream b

[bucklereed]

Aren't those just fold1 and foldMap1, specialised to NonEmpty a for the semigroup?

[Icelandjack]

You're right and same with Stream examples since Foldable1 Stream.

Data.Foldable does include

concat :: Foldable t => t [a] -> [a]
concatMap :: Foldable f => (a -> [b]) -> (t a -> [b])

so it may be worth adding them still (but obviously not as important)

concat1 :: Foldable1 f1 => f1 (NonEmpty a) -> NonEmpty a
concat1 = fold1

concatMap1 :: Foldable1 f1 => (a -> NonEmpty b) -> (f1 a -> NonEmpty b)
concatMap1 = foldMap1

[RyanGlScott]

Foldable1 is now defined in base, and semigroupoids simply re-exports Foldable1 from base. As such, this issue isn't really in scope for semigroupoids anymore. Closing.