何重和みたいなものをexpressionを取って簡単に書けるようにするマクロ

summation.clj

(defmacro sum [bindings expr]
  `(reduce + (for ~bindings ~expr)))

(macroexpand-1 '(sum [x '(1 2 3)
		      y '(4 5 6)]
		     (+ x y)))

(clojure.core/reduce
 clojure.core/+
 (clojure.core/for [x (quote (1 2 3))
		    y (quote (4 5 6))]
		   (+ x y)))

;; \sum_{x \in {1 2 3} \sum_{y \in {4 5 6} (x + y)
(sum [x '(1 2 3)
      y '(4 5 6)]
     (+ x y)) ; 63