egri-nagy

;; adapted from the Sudoku solver in `The Joy of Clojure 2nd Edition' 2014 by Michal Fogus and Chris Houser, Chater 16 Thinking Programs
(require '[clojure.core.logic :as l]         ;;the logic engine
         '[clojure.core.logic.fd :as fd])    ;;dealing with finite domains (integer numbers)

(defn latin-squares [n num-of-sols]                   ;; n - size of the square, num-fo-sols - number of solutions
  (let [tab (vec (repeatedly (* n n) l/lvar))         ;; n by n table of logic variables
        rows (partition n tab)                        ;; rows of the table
        cols (apply map vector rows)                  ;; columns of the table
        points  (fd/interval 0 (dec n))]              ;; valid entries
    (l/run num-of-sols [q]

egri-nagy

;; Caesar shift and its brute-force attack.

(def letters "abcdefghijklmnopqrstuvwxyz ")

(defn shift-map
  "A hash-map that maps letters to letters cyclically shifted by n."
  [n]
  (zipmap letters
          (take (count letters)
                (drop n (cycle letters)))))

egri-nagy

;; simple implementation of the Burrows-Wheeler transform (used in bzip2)
;; https://en.wikipedia.org/wiki/Burrows-Wheeler_transform

(defn rotations
  "All rotations (cyclic permutations) of a string s."
  [s]
  (let [n (count s)] 
    (reduce (fn [rotations i]
              (conj rotations
                    (apply str

egri-nagy

; representation of a line defined by two points
(def l [[1 2] [2 4]])

;information extracted on demand, actual calculation obscure  
(defn slope 
  [line] 
  (/
    (- (first (first line)) (first (second line)))
    (- (second (first line)) (second (second line)))))

egri-nagy

(defn merge-sort
  "sorting the given collection with merge-sort"
  [coll]
  (if (or (empty? coll) (= 1 (count coll)))
    coll
    (let [[l1 l2] (split-at (/ (count coll) 2) coll)]
      ;recursive call
      (loop [r [] l1 (merge-sort l1) l2 (merge-sort l2)]
        ;merging
        (cond (empty? l1) (into r l2) ;when l1 is exhausted