spiral.clj

(ns spiral)
  (defmacro dbg[x] `(let [x# ~x] (println "dbg:" '~x "=" x#) x#))
  (def matrix1 [[1 2 3][8 9 4][7 6 5]])
  (def matrix2 [[1 2 3 4][12 13 14 5][11 16 15 6][10 9 8 7]])
  (defn spiral-print [matrix result]
    (let [[row & rows] (seq matrix)]
      (if (seq rows)
        (recur
          (reverse (apply map vector rows))
        ;returns a new list with result + row
          (into (dbg result) (dbg row)))
        ;else
        result)))
      ;(->> [[8 9 4] [7 6 5]] (apply map vector))
      ;([8 7] [9 6] [4 5])
  (spiral-print matrix1 [])
  (spiral-print matrix2 [])

spiral=>  (spiral-print matrix2 [])
dbg: result = []
dbg: row = [1 2 3 4]
dbg: result = [1 2 3 4]
dbg: row = [5 6 7]
dbg: result = [1 2 3 4 5 6 7]
dbg: row = [8 9 10]
dbg: result = [1 2 3 4 5 6 7 8 9 10]
dbg: row = [11 12]
dbg: result = [1 2 3 4 5 6 7 8 9 10 11 12]
dbg: row = [13 14]
dbg: result = [1 2 3 4 5 6 7 8 9 10 11 12 13 14]
dbg: row = [15]
[1 2 3 4 5 6 7 8 9 10 11 12 13 14 15]