map -package:containers -package:Cabal-syntax -package:bytestring -package:base -is:exact -package:base-compat-batteries -package:blaze-html -package:incipit-base -package:monoidal-containers -package:aeson -package:dlist package:pipes is:exact

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

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