map -package:containers -package:blaze-html -is:exact -package:insert-ordered-containers -package:imports -is:exact -package:conduit -package:dlist -package:case-insensitive -package:monoidal-containers is:exact -package:charset -package:ghc package:pipes

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

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