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Implement Damerau-Levenshtein, closes #1119.

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Fetching the keyboard layout seems to be impossible to do within the JVM
without shelling out. It's probably not worth it wrt. portability.
This commit is contained in:
Jean Niklas L'orange 2013-12-30 20:09:49 +01:00
parent 248362f2e7
commit c05e102036
1 changed files with 34 additions and 20 deletions
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54
leiningen-core/src/leiningen/core/main.clj
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@ -123,25 +123,39 @@
(apply println msg))
(exit 1)))
(defn- distance [s t]
(letfn [(iters [n f start]
(take n (map second
(iterate f start))))]
(let [m (inc (count s)), n (inc (count t))
first-row (vec (range m))
matrix (iters n (fn [[j row]]
[(inc j)
(vec (iters m (fn [[i col]]
[(inc i)
(if (= (nth s i)
(nth t j))
(get row i)
(inc (min (get row i)
(get row (inc i))
col)))])
[0 (inc j)]))])
[0 first-row])]
(last (last matrix)))))
(defn- next-dist-row [s t x pprev prev]
(let [t-len (count t)
eq-chars (fn [x y] (= (nth s x) (nth t (dec y))))]
(reduce (fn [row y]
(let [min-step
(cond->
(min (inc (peek row)) ;; addition cost
(inc (get prev y)) ;; deletion cost
(cond-> (get prev (dec y)) ;; substitution cost
(not (eq-chars x y)) inc))
(and (pos? x) (pos? (dec y)) ;; check for transposition
(eq-chars x (dec y))
(eq-chars (dec x) y)
(not (eq-chars x y)))
(min (inc (get pprev (- y 2)))))] ;; transposition cost
(conj row min-step)))
[(inc x)]
(range 1 (inc t-len)))))
(defn- distance
"Returns the Damerau–Levenshtein distance between two strings."
[s t]
(let [s-len (count s)
t-len (count t)
first-row (vec (range (inc t-len)))
matrix (reduce (fn [matrix x]
(conj matrix
(next-dist-row s t x
(peek (pop matrix))
(peek matrix))))
[[] first-row]
(range s-len))]
(peek (peek matrix))))
(defn tasks
"Return a list of symbols naming all visible tasks."
@ -159,7 +173,7 @@
"leiningen." "")]]
[n (distance n task)]))
min (apply min (vals suggestions))]
(if (<= min 4)
(if (<= min 3)
(map first (filter #(= min (second %)) suggestions)))))
(defn ^:no-project-needed task-not-found [task & _]