anchor.diff:   IMapEntry
    (-key [coll] (sequences::first coll))
    (-val [coll] (sequences::rest coll))
  + ISeq
  + (-first [coll]  (sequences::first coll))
  + (-rest  [coll]  (sequences::rest coll))
    )
   
   (extend-type
  
positive.code:   ;;          (transduce xform conj to from)))
    )
  
  ;; "Returns a lazy sequence consisting of the result of applying f to
  ;;   the set of first items of each coll, followed by applying f to the
  ;;   set of second items in each coll, until any one of the colls is
  
negative.code: ;; "Evaluates the exprs in a lexical context in which the symbols in
  ;;   the binding-forms are bound to their respective init-exprs or parts
  ;;   therein. Acts as a recur target."
  ;; (defmacro loop* (bindings &rest body)
  ;;   ;; (assert-args
  ;;   ;;  (vector? bindings) "a vector for its binding"
  ;;   ;;  (even? (count bindings)) "an even number of forms in binding vector")          
  ;;   (let [vs (take 2 (drop 1 bindings))
  ;;     bs (take-nth 2 bindings)
  ;;     gs (map (fn [b] (if (symbol? b) b (gensym))) bs)
  ;;     bfs (reduce1 (fn [ret [b v g]]
  ;;                      (if (symbol? b)
  ;;                          (conj ret g v)
  ;;                          (conj ret g v b g)))
  ;;                  [] (map vector bs vs gs))]
  ;;     `(let ~bfs
  ;;        (loop* ~(vec (interleave gs gs))
  ;;               (let ~(vec (interleave bs gs))
  ;;                 ~@body)))))
  
  ;; (defmacro loop* (bindings &rest body)
  ;;   ;; (assert-args
  