A really rough first cut of a string searching function using the so-called BNDM algorithm

bndm.clj

(defn bndm [pattern string]
  "Searches for the pattern in the string using the BNDM algorithm;
   it returns a list of the indices where there is a match."
  (let [uniq-letters    (set pattern)
        indexed-letters (map-indexed vector pattern)
        bitmasks        (into {}
                          (for [c uniq-letters]
                            [c (reduce + (map (fn [[idx c']] (if (= c c') (bit-shift-left 1 idx) 0)) indexed-letters))]))]
    (loop [d 0 idx 0 acc []]
      (cond
        (= idx (dec (count string))) acc
        :else
          (let [c        (get string idx)
                bitmask  (get bitmasks c 0)
                new-d    (bit-and (bit-or (bit-shift-left d 1) 1) bitmask)
                test-bit (bit-shift-left 1 (dec (count pattern)))]
            (if (> (bit-and new-d test-bit) 0)
              (recur new-d (inc idx) (conj acc (- idx (dec (count pattern)))))
              (recur new-d (inc idx) acc)))))))

(bndm "eee" "yeeeeah")
(bndm "bananas" "there are bananas in this string")