Clojure Golf: subsets-by-card (2)
I wasn’t happy with the last one. At least this one is lazier and in increasing cardinality order.
(defn subsets-by-card [s]
(reduce (fn [ssbc x]
(map (fn [a b] (concat a (map #(conj % x) b)))
(concat ssbc [nil]) (concat [nil] ssbc)))
[[#{}]] s))
Decreasing order:
(defn subsets-by-card-reverse [s]
(reduce (fn [ssbc x]
(map (fn [a b] (concat a (map #(<ins>disj</ins> % x) b)))
(concat ssbc [nil]) (concat [nil] ssbc)))
[[<ins>(set s)</ins>]] s))
