map -package:containers -package:bytestring -package:invertible -package:basement -package:conduit -package:base -package:ghc -package:hedgehog -package:base-prelude -package:blaze-html -package:monoidal-containers -package:filepath -is:exact package:pipes is:exact

Apply a function to all values flowing downstream
map id = cat

map (g . f) = map f >-> map g