Maybe you meant to write (??) :: Functor f => f (a -> b) -> a -> f b funs ?? a = fmap ($ a) funs from lens: https://hackage.haskell.org/package/lens-5

Maybe you meant to write (??) :: Functor f => f (a -> b) -> a -> f b funs ?? a = fmap ($ a) funs from lens: https://hackage.haskell.org/package/lens-5.3.2/docs/Control-Lens-Lens.html#v:-63--63- https://hackage.haskell.org/package/lens-5.3.2/docs/Control-... This is valid definition of lift along a different, less interesting but more general axis. lift = (??) @[]