sums-to-n.clj

;; Without using partial

(defn sums-to-n? [n] 
  (fn [coll] 
    (= n (reduce + coll))))

(def f (sums-to-n? 10))
(f [1 2 3])   ; false
(f [1 2 3 4]) ; true

;; Using ```partial```

(defn sums-to-n?
  [n coll]
    (= n (reduce + coll)))

(def f (partial sums-to-n? 10))
(f [1 2 3])   ; false
(f [1 2 3 4]) ; true