enumerate-bits.clj

(defn enumerate-bits [n]
  (if  (= n 1)
    ;base case, n = 1
    [[0] [1]]

    ;normal-case, n > 1
    ;foreach bit string in enumerate-bits (- n 1) create 2 new bitstrings conjing - and 1
    (reduce
     (fn [strings assembled-string]
       (conj strings
             (conj assembled-string 0)
             (conj assembled-string 1)))
     [] 
     (enumerate-bits (- n 1)))))

test-enumerate-bits

(use '[clojure.test :as c-test])


(c-test/deftest test-enumerate-bits []
  (let [correct-vals
        [[0 0 0 0 0]
         [0 0 0 0 1]
         [0 0 0 1 0]
         [0 0 0 1 1]
         [0 0 1 0 0]
         [0 0 1 0 1]
         [0 0 1 1 0]
         [0 0 1 1 1]
         [0 1 0 0 0]
         [0 1 0 0 1]
         [0 1 0 1 0]
         [0 1 0 1 1]
         [0 1 1 0 0]
         [0 1 1 0 1]
         [0 1 1 1 0]
         [0 1 1 1 1]
         [1 0 0 0 0]
         [1 0 0 0 1]
         [1 0 0 1 0]
         [1 0 0 1 1]
         [1 0 1 0 0]
         [1 0 1 0 1]
         [1 0 1 1 0]
         [1 0 1 1 1]
         [1 1 0 0 1]
         [1 1 0 0 1]
         [1 1 0 1 0]
         [1 1 0 1 1]
         [1 1 1 0 0]
         [1 1 1 0 1]
         [1 1 1 1 0]
         [1 1 1 1 1]]]
    (is (=  (enumerate-bits 5)))))