map -package:containers -package:foldl -package:incipit-base -package:base-compat -package:basement is:exact -package:Cabal-syntax -package:hedgehog -package:invertible -package:conduit -package:bytestring -package:base-compat-batteries package:pipes

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

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