clojure sh*t

test.clj

;; Fix for the compiling problem on IntelliJ with La-Clojure:
;; Settings -> Compiler -> Clojure Compiler -> Copy Clojure source files to output...


(filter odd? [1 2 3 4 5 6])        ;; => 1 3 5
(first(filter odd? [1 2 3 4 5 6])) ;; => 1

(first '(1 2 3))                   ;; => 1
(first [1 2 3])                    ;; => 1
;(first (1 2 3))                   ;; => error ! because (1 2 3) is not interpreted as a list here
                                   ;;    the compiler expect a function as first arg of ( )
(+ 1 2 3)                          ;; => 6
(apply + [1 2 3])                  ;; => 6

(def twice
  (fn [n]
    (+ n n)))

(twice 10)                         ;; => 20

(def factorial
  (fn [n]
    (apply * (range 1 (+ n 1)))))  ;; (doc range) =>  Returns a lazy seq of nums from start (inclusive) to end
                                   ;;                 (exclusive) so its like (apply * [1 . . . n])

(factorial 5)                      ;; => 120

(def add-squares
  (fn [& numbers]
    (apply + (map * numbers numbers)))) ;; (doc map) =>  Returns a lazy sequence consisting of the result of applying f to the
                                        ;;               set of first items of each coll, followed by applying f to the set of
                                        ;;               second items in each coll, until any one of the colls is exhausted.

(add-squares 4 4)                  ;; => 32

(def prefix-of?
  (fn [candidate list]
    ( = (take (count candidate) list )
         candidate )))

(prefix-of? [1 2] [1 2 3 4])       ;; => true

(def tails
  (fn [seq]
    (map drop
      (range (inc (count seq)))    ;; (doc range) ...
      (repeat (inc (count seq)) seq ))))

(tails [1 2 3 4 5 6 7])
;; => ((1 2 3 4 5 6 7) (2 3 4 5 6 7) (3 4 5 6 7) (4 5 6 7) (5 6 7) (6 7) (7) ())

(def puzzle
  (fn [list]
    (list list))) ;; => compile error

(def puzzle
  (fn [seq]
    (list seq))) ;; => works !

(prn(puzzle '(1 2 3)))