map -package:base-prelude -package:basement -package:imports -package:containers -is:exact -package:integration -package:bytestring -package:os-string -package:charset is:exact -package:dense-linear-algebra -package:dlist -package:amazonka-core -package:base-compat package:pipes

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

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