「ClojureでNinety-Nine Lisp Problems(P01～05)」ブログ用

p01-1.clj

(defn my-last
  "Find the last box of a list."
  [xs]
  (if (>= 1 (count xs))
    xs
    (my-last (rest xs))
  )
)

p01-2.clj

(defn my-last
  "Find the last box of a list."
  [[x & xs]]
  (if (empty? xs)
    (if (nil? x) () (list x))
    (my-last xs)
  )
)

p02.clj

(defn my-but-last
  "Find the last but one box of a list."
  [xs]
  (if (>= 2 (count xs))
    xs
    (my-but-last (rest xs))
  )
)

p03-1.clj

(defn element-at
  "Find the K'th element of a list."
  [xs n]
  (cond
    (or (> 1 n) (empty? xs)) nil
    (== 1 n) (first xs)
    :else (element-at (rest xs) (dec n))
  )
)

p03-2.clj

(defn element-at
  "Find the K'th element of a list."
  [[x & xs] n]
  (cond
    (or (> 1 n) (empty? xs)) nil
    (== 1 n) x
    :else (element-at xs (dec n))
  )
)

p04-1.clj

(defn num-of-elem
  "Find the number of elements of a list."
  [xs]
  ((fn f [xs n]
    (if (empty? xs)
      n
      (f (rest xs) (inc n))
    )
  ) xs 0)
)

p04-2.clj

(defn num-of-elem
  "Find the number of elements of a list."
  [xs]
  ((fn [xs n]
    (if (empty? xs)
      n
      (recur (rest xs) (inc n))
    )
  ) xs 0)
)

p04-3.clj

(defn num-of-elem
  "Find the number of elements of a list."
  [xs]
  (#(if (empty? %1)
      %2
      (recur (rest %1) (inc %2))
  ) xs 0)
)

p05.clj

(defn reverse-list
  "Reverse a list."
  [xs]
  (#(if (empty? %1)
      %2
      (recur (rest %1) (cons (first %1) %2))
  ) xs '())
)