Data commit

Task/Emirp-primes/Swift/emirp-primes.swift

@@ -0,0 +1,46 @@
+import Foundation
+
+extension BinaryInteger {
+  var isPrime: Bool {
+    if self == 0 || self == 1 {
+      return false
+    } else if self == 2 {
+      return true
+    }
+
+    let max = Self(ceil((Double(self).squareRoot())))
+
+    for i in stride(from: 2, through: max, by: 1) where self % i == 0  {
+      return false
+    }
+
+    return true
+  }
+}
+
+func isEmirp<T: BinaryInteger>(n: T) -> Bool {
+  guard n.isPrime else {
+    return false
+  }
+
+  var aux = n
+  var revPrime = T(0)
+
+  while aux > 0 {
+    revPrime = revPrime * 10 + aux % 10
+    aux /= 10
+  }
+
+  guard n != revPrime else {
+    return false
+  }
+
+  return revPrime.isPrime
+}
+
+let lots = (2...).lazy.filter(isEmirp).prefix(10000)
+let rang = (7700...8000).filter(isEmirp)
+
+print("First 20 emirps: \(Array(lots.prefix(20)))")
+print("Emirps between 7700 and 8000: \(rang)")
+print("10,000th emirp: \(Array(lots).last!)")