gistfile1.clj

(defn col-seq [m col]
  (for [i (range (count m))] (get-in m [i col])))

(defn row-seq [m row]
  (seq (m row)))

(defn rows [m]
  (for [r (range (count m))] (row-seq m r)))

(defn cols [m] 
  (for [c (range (count (m 0)))] (col-seq m c)))

(defn vectorify 
  "takes a sequence and splits it into a matrix of the given width"
  [m-seq row-width]
  (vec (map vec (partition row-width m-seq)))) 

(defn dot-product 
  "takes two vectors, that is, sequences of numbers of equal length"
  [v1 v2]
  (reduce + 0 (map * v1 v2)))

(defn matrix-multiply [m1 m2]  
  (let [res (for [r (rows m1)
                  c (cols m2)]
              (dot-product r c))]
; the row-width of the second matrix dictates the row-width of the result
  (vectorify res (count (m2 0)))))

(def a [[1 2]
        [3 4]]) 
(def b [[5 6]  
        [7 8]])

(matrix-multiply a b)