Clojure Trie for prefix lookup

trie.clj

;; From http://stackoverflow.com/questions/1452680/clojure-how-to-generate-a-trie

(defn add-to-trie [trie x]
  (assoc-in trie x (merge (get-in trie x) {:val x :terminal true})))

(defn in-trie? [trie x]
  "Returns true if the value x exists in the specified trie."
  (:terminal (get-in trie x) false))

(defn prefix-matches [trie prefix]
  "Returns a list of matches with the prefix specified in the trie specified."
  (keep :val (tree-seq map? vals (get-in trie prefix))))

(defn build-trie [coll]
  "Builds a trie over the values in the specified seq coll."
  (reduce add-to-trie {} coll))

(def coll [#{"a" "b" "c"} #{"a" "b"} #{"c" "d"} #{"c" "d" "e"} #{"e" "d" "a"}]) 
(def trie (build-trie (map (comp sort vec) coll)))

user=> (prefix-matches trie ["a"])
(("a" "b") ("a" "b" "c") ("a" "d" "e"))
user=> (prefix-matches trie ["a" "b"])
(("a" "b") ("a" "b" "c"))