(use '[clojure.contrib.str-utils :only (re-split str-join)])

(def test-sentence
  "Perl is a high-level, general-purpose, interpreted, dynamic programming language.")

(defn uniq-phrases
  "Find unique phrases of the given lengths (def 2-4 words; max may be omitted)"
  ([sentence] (uniq-phrases sentence 2 4))
  ([sentence len] (uniq-phrases sentence len len))
  ([sentence min-len max-len]
    (let [words (re-split #"\s+" sentence)
          pairs (set (mapcat #(partition %1 1 words) (range min-len (inc max-len))))]
      (map #(str-join " " %) pairs))))

(defn print-phrases [p]
  (println (str-join "\n" (sort p))))

(print-phrases (uniq-phrases test-sentence 2 9))

; user=> (time (print-phrases (uniq-phrases test-sentence 4 4)))
; Perl is a high-level,
; a high-level, general-purpose, interpreted,
; general-purpose, interpreted, dynamic programming
; high-level, general-purpose, interpreted, dynamic
; interpreted, dynamic programming language.
; is a high-level, general-purpose,
; "Elapsed time: 1.227 msecs"