Calculating euclidean distance using tree composition

tree-comp-each.clj

(def x [1 2])
(def y [4 5])

(defn- tree-comp-each [root branch & leaves]
 (apply 
  root (map branch leaves)))

(defn euclidean-distance
	[a b]
	{:pre [(= (count a) (count b))]}
	(sqrt
  	(apply
   		tree-comp-each
   		+ 
  		(fn [[x y]] 
    		(pow (- x y) 2))
  		(map vector a b))))