fold-right and reduce-right in Clojure

fold-right.clj

(use 'clojure.test)

(defn fold-right [f z coll]
  (loop [[c & cs] coll rvsd '()]
    (if (nil? c)
        (loop [acc z [r & rs] rvsd]
          (if r (recur (f r acc) rs) acc))
        (recur cs (cons c rvsd)))))

(defn reduce-right [f coll]
  (loop [[c & cs] coll rvsd '()]
    (if (nil? cs)
        (loop [acc c [r & rs] rvsd]
          (if r (recur (f r acc) rs) acc))
        (recur cs (cons c rvsd)))))

(deftest test-fold-right
  (are [result expected] (= result expected)
    (fold-right - 2 '(3 1 4 1 5 9)) ; (- 3 (- 1 (- 4 (- 1 (- 5 (- 9 2))))))
      3
    (fold-right #(cons (* 2 %) %2) '() '(3 1 4 1 5 9 2)) ; map #(* 2 %)
      '(6 2 8 2 10 18 4)
    (fold-right #(concat %2 (list %)) '() '(3 1 4 1 5 9 2)) ; reverse
      '(2 9 5 1 4 1 3)
    ))

(deftest test-reduce-right
  (are [result expected] (= result expected)
    (reduce-right - '(3 1 4 1 5 9 2))
      3
    (reduce-right #(cons (* 2 %) (if (seq? %2) %2 (list (* 2 %2)))) '(3 1 4 1 5 9 2))
      '(6 2 8 2 10 18 4)
    (reduce-right #(concat (if (seq? %2) %2 (list %2)) (list %)) '(3 1 4 1 5 9 2))
      '(2 9 5 1 4 1 3)
    ))

Updated not to eat large stack but heap.

user=> (fold-right - 0 (range 1000000))
-500000
user=> (fold-right - 0 (range 2000000))
OutOfMemoryError Java heap space clojure.lang.ArrayChunk.dropFirst (ArrayChunk.java:54)

How stupid have I been!
'f' doesn't vary in the accumulated list.
We only have to keep 1st operands of 'f' in reversed order in a list.

user=> (fold-right - 0 (range 2000000))
-1000000