map -package:containers -package:charset -package:invertible -is:exact -package:Cabal-syntax -package:incipit-base is:exact -package:insert-ordered-containers -package:amazonka-core -package:hedgehog -package:basement -package:base-compat package:pipes

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

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