map is:exact -package:text -package:containers -package:base-prelude -package:foldl -package:case-insensitive -package:bytestring -package:Cabal-syntax -package:invertible -package:incipit-base -package:base -package:filepath -package:blaze-html package:basement
Map all element a from a block to a new block of b
Map all elements in a list