map -package:containers -package:foldl -package:incipit-base -package:aeson -package:bytestring -package:base-prelude -package:basement -is:exact -package:charset is:exact -package:base-compat-batteries -package:dense-linear-algebra package:pipes

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

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