map -package:containers -package:foldl -package:incipit-base -package:base-compat -package:insert-ordered-containers -package:blaze-html -package:monoidal-containers -package:hedgehog -package:invertible -package:bytestring -package:dlist package:pipes is:exact

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

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