map -package:containers -package:charset -package:amazonka-core -package:basement -package:case-insensitive -package:foldl -package:ghc -is:exact -package:hedgehog -package:psqueues -package:base-prelude is:exact -package:blaze-html -package:regex-tdfa package:pipes

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

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