Decimal to Roman Numeral converter, 2

destructuring2.clj

(let [ [fst snd] (filter odd? [1 2 3 4 5])]
  (println fst snd))
=> 1 3

destructuring3.clj

(filter #(>= 4 (first %)) mapping)
=> ([4 "IV"] [1 "I"])

destructuring4.clj

(let [ [ [n c] ] (filter ...)]
  (recur ...))

filter.clj

(filter #(>= i (first %)) mapping)

loop1.clj

(defn roman-numeral [i]
  (loop [i i s ""]
    ...)

recur1.clj

(recur (- i n) (str s c))

recur2.clj

(defn- roman-helper [i s]
  (if (zero? i)
    s
    (let [[[n c]] (filter #(>= i (first %)) mapping)]
      (roman-helper (- i n) (str s c)))))

(defn roman-numeral [i]
  (roman-helper i ""))

recur3.clj

(defn- roman-helper [i s]
  (if (zero? i)
    s
    (let [[[n c]] (filter #(>= i (first %)) mapping)]
      (recur (- i n) (str s c)))))

(defn roman-numeral [i]
  (roman-helper i ""))

recur4.clj

(defn roman-numeral [i]
  (let [roman-helper (fn [i s]
                       (if (zero? i)
                         s
                         (let [[[n c]] (filter #(>= i (first %)) mapping)]
                           (recur (- i n) (str s c)))))]
    (roman-helper i "")))

roman2.clj

(defn roman-numeral [i]
  (loop [i i s ""]
    (if (zero? i)
      s
      (let [[[n c]] (filter #(>= i (first %)) mapping)]
        (recur (- i n) (str s c))))))