add TODO: about dissoc’s handling of special inputs which are not maps, like :top and :fail.
handle :fail and :top as potential inputs to the exception generation function
add TODO/comment
add “nero”
(fo <list>) => (map #(fo %) <list>)
handle a parse tree (a DAG) which is the output of (parse) as input to parse, e.g.:

 (parse "il" (parse "gatto nero"))