map -package:containers -package:blaze-html -is:exact -package:bytestring -package:dlist -is:exact -package:integration -package:filepath -package:Cabal-syntax -package:hedgehog -package:dense-linear-algebra -package:amazonka-core -package:os-string package:pipes is:exact

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

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