map is:exact -package:text -package:charset -package:dense-linear-algebra -package:amazonka-core -package:basement -package:incipit-base -package:monoidal-containers -package:dlist -package:insert-ordered-containers -package:hedgehog -package:base-prelude package:pipes

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

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