map -package:containers -package:blaze-html -is:exact -package:insert-ordered-containers -package:monoidal-containers -package:dlist -package:base-compat-batteries -package:Cabal-syntax -package:imports -package:dense-linear-algebra is:exact package:pipes

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

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