Accumulator generator

Sep 19 2015 | tags: python, clojure

Paul Graham’s accumulator generator. foo generates an accumulator function and returns it.

In python:

class foo:
    def __init__(self, n):
        self.n = n
    def __call__(self, i):
        self.n += i
        return self.n

x = foo(1) # 1
x(5) # 1+5
foo(3)
print (x(2.3)) # 1+5+2.3

In clojure:

(defn foo [n]
  (let [acc (atom n)]
    (fn [i] (swap! acc + i))))

(def x (foo 1)) ; 1
(x 5) ; 1+5
(println (x 2.3)) ; 1+5+2.3