map -package:containers -package:Cabal-syntax -package:base-compat -package:base-prelude -package:invertible -package:foldl -package:amazonka-core -package:blaze-html -package:monoidal-containers is:exact -package:os-string package:pipes

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

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