map -package:containers -package:base-compat -package:dlist -package:charset -package:integration -package:blaze-html -package:amazonka-core -package:insert-ordered-containers -package:dense-linear-algebra -package:incipit-base -package:monoidal-containers -package:bytestring package:pipes is:exact

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

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