gistfile1.clj

(defn projections-on-section
  "From a map of {key, {:entries {s [sx sy] ...} ...}} and 's', return a map of {key, [sx sy]}"
  [all-trails section]
  {:pre  [(map? all-trails)]
   :post [(map? %) (every? key? (keys %)) (every? vpoint? (vals %))]}
  (let [trails (filter #(contains? (:entries (val %)) section) all-trails)]
    (with-meta
      (into {} (map (fn [t]
		      (let [id (key t), trail (val t)
			    entries (get (:entries trail) section)]
			{id (->vpoint (first entries))}))
		    trails))
      {:section section})))

(defn projections-on-section
"From a map of {key, {:entries {s [sx sy] ...} ...}} and 's', return a map of {key, [sx sy]}"
[all-trails section]
{:pre [(map? all-trails)]
:post [(map? %) (every? key? (keys %)) (every? vpoint? (vals %))]}
(let [trails (filter #(contains? (:entries (val %)) section) all-trails)](with-meta
%28into {}
;; %28map %28fn [t]
;; %28let [id %28key t%29, trail %28val t%29
;; entries %28get %28:entries trail%29 section%29]
;; {id %28->vpoint %28first entries%29%29}%29%29
;; trails%29
%28for [[id trail] trails]
{id %28->vpoint %28first %28get %28:entries trail%29 section%29%29%29}%29
%29
{:section section})))