map is:exact -package:bytestring -package:foldl -package:Cabal-syntax -package:dlist -package:amazonka-core -package:containers -package:ghc -package:base-compat-batteries -package:base-compat -package:monoidal-containers package:pipes

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

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