gistfile1.txt

(defmacro fold 
  "sugar on reduce, similar to how 'for' is a nicer version of 'map'.

  init is a symbol that evaluates to a value (local or var) or a vector of a symbol and an initial value. In the loop, init is bound to the result of the previous loop.

Binding can take any arguments supported by for, but should only bind one variable.
"
;;   (fold r [i (range 10)]   ;; existing symbol
;;       (+ r i))

;; (fold [r 0] [i (range 10)] ;; define new local
;;        (+ r i))
  [initial binding & body]
  (let [[init-sym init-val] (if (symbol? initial)
                              [initial initial]
                              initial)]
    `(let [~init-sym ~init-val]
       (reduce (fn [~init-sym ~(first binding)]
                 ~@body) ~init-sym ~@(rest binding)))))