Merge pull request #3818 from tylerw/tw/challenge-106

Ch106 (Clojure): Tasks 1 & 2

1 files changed, 43 insertions, 0 deletions

diff --git a/challenge-106/tyler-wardhaugh/clojure/src/tw/weekly/c106/t2.clj b/challenge-106/tyler-wardhaugh/clojure/src/tw/weekly/c106/t2.clj
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+++ b/challenge-106/tyler-wardhaugh/clojure/src/tw/weekly/c106/t2.clj
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+(ns tw.weekly.c106.t2
+  (:require [clojure.edn :as edn]
+            [clojure.math.numeric-tower :refer [abs]]))
+
+;;;
+; Task description for TASK #2 › Decimal String
+;;;
+(def DEFAULT-INPUT [1 3])
+
+(defn- decimal-string-recurring
+  "Covert the given n[umerator] and d[enominator] (which must be known to
+  have a recurring fractional result) into a decimal string where the recurring
+  fractional is put in parenthesis."
+  [n d]
+  (loop [remainder (abs (rem n d))
+         cache {}
+         result []]
+    (if (not (or (zero? remainder) (cache remainder)))
+      (recur (rem (* 10 remainder) d)
+             (assoc cache remainder (count (apply str result)))
+             (conj result (quot (* 10 remainder) d)))
+      (let [[lead recurrence] (->> result (split-at (get cache remainder 0)))
+            whole (quot n d)
+            pieces (concat [whole \.] lead [\(] recurrence [\)])]
+        (apply str pieces)))))
+
+(defn decimal-string
+  "Covert the given n[umerator] and d[enominator] into a decimal string where any
+  recurring fractional is put in parenthesis."
+  [n d]
+  (try (str (/ (bigdec n) d))
+       (catch ArithmeticException _
+         ; BigDecimal throws this exception when the result cannot be
+         ; represented with the 'UNLIMITED' precision (the default), i.e.,
+         ; there is a recurring fractional result
+         (decimal-string-recurring n d))))
+
+(defn -main
+  "Run Task 2 with a given N and D, defaulting to the example given in the task
+  description."
+  [& args]
+  (let [[N D] (or (some->> args (take 2) (map edn/read-string)) DEFAULT-INPUT)]
+    (println (decimal-string N D))))