September 2017 Update

Task/Extensible-prime-generator/Kotlin/extensible-prime-generator.kotlin

@@ -0,0 +1,36 @@
+// version 1.1.2
+// compiled with flag -Xcoroutines=enable to suppress 'experimental' warning
+
+import kotlin.coroutines.experimental.*
+
+fun isPrime(n: Int) : Boolean {
+    if (n < 2) return false
+    if (n % 2 == 0) return n == 2
+    if (n % 3 == 0) return n == 3
+    var d : Int = 5
+    while (d * d <= n) {
+        if (n % d == 0) return false
+        d += 2
+        if (n % d == 0) return false
+        d += 4
+    }
+    return true
+}
+
+fun generatePrimes() =
+    buildSequence {
+        yield(2)
+        var p = 3
+        while (p <= Int.MAX_VALUE) {
+           if (isPrime(p)) yield(p)
+           p += 2
+        }
+    }
+
+fun main(args: Array<String>) {
+    val primes = generatePrimes().take(10000) // generate first 10,000 primes
+    println("First 20 primes : ${primes.take(20).toList()}")
+    println("Primes between 100 and 150 : ${primes.filter { it in 100..150 }.toList()}")
+    println("Number of primes between 7700 and 8000 = ${primes.filter { it in 7700..8000 }.count()}")
+    println("10,000th prime = ${primes.last()}")
+}