Discussion on: Daily Challenge #249 - Incremental Changes

[@nobody]

Clojure - Level 2 🌟🌟

(ns dailyChallenge.IncrementalChange249
  (^:level2))

;; recursive function w/ tail-end optimization
(defn algo [number, step, iterations]
  {:pre (>= iterations 1)}
    (let [accum 
            (loop [ result [number] itr iterations]
              (if (= 1 itr)
                (conj result step)
                (recur result (dec itr))))]
       (apply + accum))


(deftest test-algo
  (is (= 52 (algo 2 5 10))
  (is (= 35 (algo 17, 3, 6)))

(run-tests 'test-algo)

[Paula Gearon]

Compared to your "level 1", this is more like the question asked, since it asks for an algorithm rather than the answer. (I totally agree that it should be (+ number (* step iterations))).

In Clojure it's usually better to preference core functions, followed by reduce, followed by loop/recur.

The clojure.core function approach is just:

(defn algo
 [number step iterations]
 (->> number
      (iterate (partial + step))
      (drop iterations)
      first))

But that's really using iterate to do the algorithm part. So reduce might be more in the spirit of things. It's shorter too 🙂

(defn algo
 [number step iterations]
 (->> (repeat step)
      (take iterations)
      (reduce + number)))

[@nobody]

Awesome breakdown! Thanks Paula. 🙏🏿

I feel like you're right on the hierarchy of abstraction to use for Clojure functions (there's just so many, and many of them are composed)._

I could've just used pure-recursion without loop/recur but I don't get the power of the AST's tail-end optimizer for loops. Thank you for reminding me of the thread-macro.