September 2017 Update

Task/Probabilistic-choice/Kotlin/probabilistic-choice.kotlin

@@ -0,0 +1,38 @@
+// version 1.0.6
+
+fun main(args: Array<String>) {
+    val letters  = arrayOf("aleph", "beth", "gimel", "daleth", "he", "waw", "zayin", "heth")
+    val actual   = IntArray(8)
+    val probs    = doubleArrayOf(1/5.0, 1/6.0, 1/7.0, 1/8.0, 1/9.0, 1/10.0, 1/11.0, 0.0)
+    val cumProbs = DoubleArray(8)
+
+    cumProbs[0] = probs[0]
+    for (i in 1..6) cumProbs[i] = cumProbs[i - 1] + probs[i]
+    cumProbs[7] = 1.0
+    probs[7] = 1.0 - cumProbs[6]
+    val n = 1000000
+    (1..n).forEach {
+        val rand = Math.random()
+        when {
+             rand <= cumProbs[0] -> actual[0]++
+             rand <= cumProbs[1] -> actual[1]++
+             rand <= cumProbs[2] -> actual[2]++
+             rand <= cumProbs[3] -> actual[3]++
+             rand <= cumProbs[4] -> actual[4]++
+             rand <= cumProbs[5] -> actual[5]++
+             rand <= cumProbs[6] -> actual[6]++
+             else                -> actual[7]++
+        }
+    }
+
+    var sumActual = 0.0
+    println("Letter\t Actual    Expected")
+    println("------\t--------   --------")
+    for (i in 0..7) {
+        val generated = actual[i].toDouble() / n
+        println("${letters[i]}\t${String.format("%8.6f   %8.6f", generated, probs[i])}")
+        sumActual += generated
+    }
+    println("\t--------   --------")
+    println("\t${"%8.6f".format(sumActual)}   1.000000")
+}