September 2017 Update

Task/Fractran/Kotlin/fractran.kotlin

@@ -0,0 +1,45 @@
+// version 1.1.3
+
+import java.math.BigInteger
+
+class Fraction(val num: BigInteger, val denom: BigInteger) {
+    operator fun times(n: BigInteger) = Fraction (n * num, denom)
+
+    fun isIntegral() = num % denom == BigInteger.ZERO
+}
+
+fun String.toFraction(): Fraction {
+    val split = this.split('/')
+    return Fraction(BigInteger(split[0]), BigInteger(split[1]))
+}
+
+val BigInteger.isPowerOfTwo get() = this.and(this - BigInteger.ONE) == BigInteger.ZERO
+
+val log2 = Math.log(2.0)
+
+fun fractran(program: String, n: Int, limit: Int, primesOnly: Boolean): List<Int> {
+    val fractions = program.split(' ').map { it.toFraction() }
+    val results = mutableListOf<Int>()
+    if (!primesOnly) results.add(n)
+    var nn = BigInteger.valueOf(n.toLong())
+    while (results.size < limit) {
+        val frac = fractions.find { (it * nn).isIntegral() } ?: break
+        nn = nn * frac.num / frac.denom
+        if (!primesOnly) {
+           results.add(nn.toInt())
+        }
+        else if (primesOnly && nn.isPowerOfTwo) {
+           val prime = (Math.log(nn.toDouble()) / log2).toInt()
+           results.add(prime)
+        }
+    }
+    return results
+}
+
+fun main(args: Array<String>) {
+    val program = "17/91 78/85 19/51 23/38 29/33 77/29 95/23 77/19 1/17 11/13 13/11 15/14 15/2 55/1"
+    println("First twenty numbers:")
+    println(fractran(program, 2, 20, false))
+    println("\nFirst twenty primes:")
+    println(fractran(program, 2, 20, true))
+}