Data update

Task/Additive-primes/Scala/additive-primes.scala

@@ -0,0 +1,26 @@
+def isPrime(n: Int): Boolean = {
+  @annotation.tailrec
+  def checkDivisor(d: Int): Boolean = {
+    if (d * d > n) true
+    else if (n % d == 0) false
+    else checkDivisor(d + 2)
+  }
+
+  if (n < 2) false
+  else if (n == 2 || n == 3) true
+  else if (n % 2 == 0 || n % 3 == 0) false
+  else checkDivisor(5)
+}
+
+private def digitSum(n: Int): Int = n.toString.map(_ - '0').sum
+
+private def additivePrime(n: Int): Boolean = isPrime(n) && isPrime(digitSum(n))
+
+private def testAdditivePrime(max: Int): Unit = {
+  val result = (2 to max).filter(additivePrime)
+  println(result.mkString(", "))
+  println(s"Found ${result.length} additive primes less than 500.")
+}
+
+@main def main(): Unit =
+  testAdditivePrime(500)