map is:exact -package:text -package:dense-linear-algebra -package:dlist -package:charset -package:foldl -package:containers -package:aeson -package:monoidal-containers -package:base-compat-batteries -package:case-insensitive -package:blaze-html -package:invertible package:basement
Map all element a from a block to a new block of b
Map all elements in a list