map -package:Cabal -package:base -package:case-insensitive -package:bytestring -package:blaze-html -package:hedgehog is:exact -package:containers -package:aeson -package:filepath package:ghc

Apply a function to each element of a Stream, lazily
Map a function over all values in the map.
map (++ "x") (fromList [(5,"a"), (3,"b")]) == fromList [(3, "bx"), (5, "ax")]
map f s is the set obtained by applying f to each element of s. It's worth noting that the size of the result may be smaller if, for some (x,y), x /= y && f x == f y