foldmapvia.hs

{-# LANGUAGE AllowAmbiguousTypes #-}

import Data.Coerce
import Data.Foldable

foldMapVia
  :: forall b f r a
   . Coercible r b
  => Monoid b
  => Foldable f
  => (a -> r)
  -> f a
  -> r
foldMapVia f = coerce @b @r . foldMap (coerce @r @b . f)

foldVia
  :: forall b f r
   . Coercible r b
  => Monoid b
  => Foldable f
  => f r
  -> r
foldVia = foldMapVia @b id