Ch147 (Clojure): Task #1

2 files changed, 40 insertions, 0 deletions

diff --git a/challenge-147/tyler-wardhaugh/clojure/src/c147/t1.clj b/challenge-147/tyler-wardhaugh/clojure/src/c147/t1.clj
new file mode 100644
index 0000000000..dd9e87c6c0
--- /dev/null
+++ b/challenge-147/tyler-wardhaugh/clojure/src/c147/t1.clj
@@ -0,0 +1,29 @@
+(ns c147.t1
+  (:require [com.hypirion.primes :as p]))
+
+(def TARGET 20)
+
+(defn digits->n
+  [digits]
+  (parse-long (apply str digits)))
+
+(defn left-truncatable-prime?
+  [n]
+  (let [digits (-> n str seq)]
+    (when (not-any? #(= \0 %) digits)
+      (->> (iterate rest digits)
+           (drop 1)
+           (take-while seq)
+           (map digits->n)
+           (every? p/prime?)))))
+
+(defn left-truncatable-primes
+  [n]
+  (->> (p/primes)
+       (filter left-truncatable-prime?)
+       (take n)))
+
+
+(defn -main
+  [& _]
+  (println (left-truncatable-primes TARGET)))
diff --git a/challenge-147/tyler-wardhaugh/clojure/test/c147/t1_test.clj b/challenge-147/tyler-wardhaugh/clojure/test/c147/t1_test.clj
new file mode 100644
index 0000000000..fc527438d0
--- /dev/null
+++ b/challenge-147/tyler-wardhaugh/clojure/test/c147/t1_test.clj
@@ -0,0 +1,11 @@
+(ns c147.t1-test
+  (:require [clojure.test :refer [deftest is testing]]
+            [c147.t1 :as t1]))
+
+; source: https://oeis.org/A024785
+(def FIRST-20-LEFT-TRUNCATABLE-PRIMES
+  [2, 3, 5, 7, 13, 17, 23, 37, 43, 47, 53, 67, 73, 83, 97, 113, 137, 167, 173, 197])
+
+(deftest target
+  (testing "Target identified in task description"
+    (is (= FIRST-20-LEFT-TRUNCATABLE-PRIMES (t1/left-truncatable-primes t1/TARGET)))))