map -package:containers -package:charset -package:invertible -is:exact -package:dense-linear-algebra -package:insert-ordered-containers -is:exact -package:monoidal-containers is:exact -package:os-string -package:Cabal-syntax -package:base-compat package:pipes

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

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