A very simple implementation of Markov chaining in Clojure.

SimpleMarkovChain.clj

(defn model-from-sequence
  "Returns a transition matrix of 'depth' from 'sequence'"
  [depth sequence]
  (loop [accum {} chunks (partition (inc depth) 1 (seq sequence))]
           (if (seq? chunks)
             (let [chunk  (first chunks)
               prefix (drop-last chunk)
               suffix (last chunk)]
               (recur (assoc accum prefix (conj (get accum prefix []) suffix)) (next chunks)))
             accum)))

(defn chain
  "Returns a lazy Markov chain starting with 'current' using matrix 'trans'"
  [current trans]
  (if-let [transitions (trans current)]
    (cons (first current)
          (lazy-seq (chain (concat (rest current) [(rand-nth transitions)]) trans)))
    current))