map -package:containers -package:ghc -package:amazonka-core -package:dense-linear-algebra -is:exact -package:case-insensitive -package:invertible is:exact -package:base -package:hedgehog -package:base-compat-batteries -package:dlist -package:os-string package:pipes

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

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