99lisp.clj

(defn my-last [a]
  "P01 - find the last box of a list"
  ((fn my-last-recur [b c]
    (if (empty? c)
      b
      (my-last-recur (first c) (rest c))
      )) 
    (first a) 
    (rest a))
  )


(defn my-last2 [a]
  "P01 - find the last box of a list"
  (if ((= 1 (count a)))
    (first a)
    (recur (rest a)))
  )


(defn my-last3 [a]
  "P01 - find the last box of a list"
  (if (next a))
    (first a)
    (recur (rest a)))
  )

(defn my-but-last [a]
  "P02 - find the last but one box of a list"
  (if (= 2 (count a))
    a
    (recur (rest a)))
  )


(defn element-at [a n]
  "P03 - find the K'th element of a list"
    (if (zero? n)
      (first a)
      (recur (rest a) (dec n)))
    )

(defn my-count [a]
  "P04 - Find the number of elements of a list"
  (loop [r a
         n 0]
    (if (empty? r)
      n
      (recur (rest r) (inc n))))
  )

(defn my-count2 [a]
  "P04 - Find the number of elements of a list"
  (reduce (fn [a b] (inc a)) 0 a)
  )

(defn my-reverse [a]
  "P05 - Reverse a list"
  (reduce #(cons %2 %1) '() a)
  )

(defn palindrome? [a]
  "P06 - Find out whether a list is a palindrome"
  (= a (my-reverse a)) 
  )

(defn my-flatten [a]
  "P07 - Fatten a nested list structure"
  (reduce (fn [acc b]
    (if (seq? b)
      (concat acc (my-flatten b))
      (concat acc (list b))) 
      ) '() a)
  )

(defn my-compress [a]
  "P08 - Eleminate consecutive duplicates of list elements"
  (reduce
    (fn [acc b]
      (if (= (last acc) b)
        acc
        (concat acc (list b)) ))
    '() a)
  )