map is:exact -package:text -package:amazonka-core -package:basement -package:bytestring -package:containers -package:dense-linear-algebra -package:monoidal-containers -package:case-insensitive -package:psqueues -package:invertible -package:charset package:pipes

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

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