map -package:containers -package:base-compat-batteries -package:foldl -package:Cabal-syntax -package:bytestring -package:dlist -package:base-compat -package:hedgehog -package:imports -is:exact -package:monoidal-containers package:pipes is:exact

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

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