Clojure

Clojure

编程范型	多范型，函数式
发行时间	2007
設計者	Rich Hickey
最新发行时间	1.6 / 2014年3月25日 (2014-03-25)
型態系統	动态类型，强类型
啟發語言	Common Lisp, Erlang, Haskell, ML, Prolog, Scheme, Java
Platform	JVM, CLR
作業系統	跨平台
許可證	Eclipse公共许可证
常用文件扩展名	.clj
網站	http://clojure.org
维基教科书中有关Clojure Programming的电子教程

Clojure（發音類似"closure"）是一套現代的Lisp語言的動態語言版。它是一个函数式多用途的语言。

Clojure可以執行於Java虛擬機，通用語言運行時以及JavaScript引擎之上。與其他Lisp一樣，Clojure認為同像性，同時擁有複雜的巨集。

§語言哲學

因为 Hickey 希望有一个提供函数式编程和并发的现代Lisp实现，所以他开发了 Clojure 语言。

§語法

Clojure 的語法和其他的Lisp一樣，都是建立在 S-expression 之上。

§範例

Hello world:

(println "Hello, world!")

定义一个函数：

(defn square [x]
  (* x x))
 
(square 5) ; return 25

使用Java Swing 库的 GUI Hello World:

(javax.swing.JOptionPane/showMessageDialog nil "Hello World")

§用Clojure解数独的程序

(def board
  [[5 3 0 0 7 0 0 0 0]
   [6 0 0 1 9 5 0 0 0]
   [0 9 8 0 0 0 0 6 0]
   [8 0 0 0 6 0 0 0 3]
   [4 0 0 8 0 3 0 0 1]
   [7 0 0 0 2 0 0 0 6]
   [0 6 0 0 0 0 2 8 0]
   [0 0 0 4 1 9 0 0 5]
   [0 0 0 0 8 0 0 7 9]])
 
(defn board-rows [board]
  (let [full-set (set (range 1 10))
        exists (mapv #(remove (partial == 0) %) board)]
    (mapv #(clojure.set/difference full-set (set %)) exists)))
 
(defn board-cols [board]
  (let [board-v (for [i (range 9)]
                  (map #(% i) board))]
    (board-rows board-v)))
 
(defn board-blks [board]
  (let [board-b (for [i (range 3)
                      j (range 3)]
                  (for [k (range 3)
                        l (range 3)
                        :let [x (+ k (* i 3))
                              y (+ l (* j 3))]]
                    (get-in board [x y])))]
    (board-rows board-b)))
 
(defn board-tofill [board]
  (vec (for [i (range 9)
             j (range 9)
             :let [v (get-in board [i j])]
             :when (== v 0)]
         [i j])))
 
(defn blk-ix [x y]
  (let [i (quot x 3)
        j (quot y 3)]
    (+ j (* i 3))))
 
(defn fill-cand [x y rows cols blks]
  (let [row (get rows x)
        col (get cols y)
        blk (get blks (blk-ix x y))]
    (clojure.set/intersection row col blk)))
 
(defn solve-sudoku
  ([tofill rows cols blks board]
     (if (empty? tofill)
       board
       (let [cands (for [i (range (count tofill))
                         :let [[x y] (get tofill i)
                               cand (fill-cand x y rows cols blks)]]
                     [i x y cand])
             [mk x y min-cand] (apply min-key #(count (peek %)) cands)
             tofill-update (vec (concat (take mk tofill) (drop (inc mk) tofill)))
             ]
         (when (not (empty? min-cand))
           (apply concat
                  (for [cand min-cand
                        :let [cand-set #{cand}
                              remove-cand (fn [s i] (update-in s [i] #(clojure.set/difference % cand-set)))
                              rows-update (remove-cand rows x)
                              cols-update (remove-cand cols y)
                              blks-update (remove-cand blks (blk-ix x y))
                              board-update (assoc-in board [x y] cand)
                              ]]
                    (solve-sudoku tofill-update rows-update cols-update blks-update board-update))))
         )))
  ([board]
     (let [tofill (board-tofill board)
           rows (board-rows board)
           cols (board-cols board)
           blks (board-blks board)
           ]
       (remove nil? (solve-sudoku tofill rows cols blks board))
       )))
 
(solve-sudoku board) ; result: ([5 3 4 6 7 8 9 1 2] [6 7 2 1 9 5 3 4 8] [1 9 8 3 4 2 5 6 7] [8 5 9 7 6 1 4 2 3] [4 2 6 8 5 3 7 9 1] [7 1 3 9 2 4 8 5 6] [9 6 1 5 3 7 2 8 4] [2 8 7 4 1 9 6 3 5] [3 4 5 2 8 6 1 7 9])

§巨集

作为一种Lisp方言，Clojure支持巨集 。下面的巨集將中缀表达式遞迴展開成Lisp的前缀表达式。

(defmacro recursive-infix [[x op y]]
  `(~op
    ~(if (seq? x)
       `(recursive-infix ~x)
       x)
    ~(if (seq? y)
       `(recursive-infix ~y)
       y)))

§编辑器/IDE

• Emacs + NREPL + Lein

• LightTable

§外部連結

您可以在維基教科書中查找此百科条目的相關電子教程：

Clojure Programming

• Clojure 官方站
• GitHub code repository for Clojure
• A comprehensive overview of Clojure
• Full Disclojure - Screencast
• Clojure cheatsheet
• Clojure Handbook
• Clojure toolbox: Clojure的软件包分类列表