Roman Numerals - kata @socrates 2019

roman_numerals.clj

(ns roman-numerals.core-test
  (:require [clojure.test :refer :all]))

(def roman-digit->arabic
  {\I 1
   \V 5
   \X 10
   \L 50
   \C 100})

;; problem: the accumulation is arabic, but negagtive are in the romain world
(defn arabic-compromiser [result list-of-nums]
  (cond
    (empty? list-of-nums) result
    (= 1 (count list-of-nums)) (+ result (first list-of-nums))
    :else (let [first-num (first list-of-nums)
                second-num (second list-of-nums)
                rest-list-nums (rest list-of-nums)]
            (if (>= first-num second-num)
              (recur (+ result first-num) rest-list-nums)
              (recur (+ result (- second-num first-num)) (rest rest-list-nums))))))


(defn roman->arabic [roman]
  (->> roman
       (map roman-digit->arabic)
       (arabic-compromiser 0)))

(deftest roman->arabic-should
  (testing "tranlate roman digits to arabic"
    (is (= 1 (roman->arabic "I")))
    (is (= 5 (roman->arabic "V")))
    (is (= 10 (roman->arabic "X")))
    (is (= 50 (roman->arabic "L")))
    (is (= 100 (roman->arabic "C"))))

  (testing "add repeated digits that are equals"
    (is (= 2 (roman->arabic "II")))
    (is (= 3 (roman->arabic "III")))
    (is (= 20 (roman->arabic "XX")))
    (is (= 30 (roman->arabic "XXX")))
    (is (= 200 (roman->arabic "CC")))
    (is (= 300 (roman->arabic "CCC"))))


  (testing "add repeated digits that are decreasing order"
    (is (= 15 (roman->arabic "XV")))
    (is (= 110 (roman->arabic "CX"))))


  (testing "subtracts digits that are in increasing order"
    (is (= 4 (roman->arabic "IV")))
    (is (= 9 (roman->arabic "IX")))
    (is (= 90 (roman->arabic "XC")))))