map -package:containers -package:aeson -package:base-compat-batteries -package:basement -package:pipes -package:invertible -package:foldl package:dlist is:exact

map f xs is the DList obtained by applying f to each element of xs. <math>(length (toList xs)). map obeys the law:
toList (map f xs) = map f (toList xs)
map f xs is the DNonEmpty obtained by applying f to each element of xs. <math>(length (toNonEmpty xs)). map obeys the law:
toNonEmpty (map f xs) = map f (toNonEmpty xs)