June 2018 Update

Task/Active-object/Kotlin/active-object.kotlin

@@ -0,0 +1,69 @@
+// version 1.2.0
+
+import kotlin.math.*
+
+typealias Function = (Double) -> Double
+
+/**
+ * Integrates input function K over time
+ * S + (t1 - t0) * (K(t1) + K(t0)) / 2
+ */
+class Integrator {
+    private val start: Long
+    private @Volatile var running = false
+    private lateinit var func: Function
+    private var t0 = 0.0
+    private var v0 = 0.0
+    private var sum = 0.0
+
+    constructor(func: Function) {
+        start = System.nanoTime()
+        setFunc(func)
+        Thread(this::integrate).start()
+    }
+
+    fun setFunc(func: Function) {
+        this.func = func
+        v0 = func(0.0)
+        t0 = 0.0
+    }
+
+    fun getOutput() = sum
+
+    fun stop() {
+        running = false
+    }
+
+    private fun integrate() {
+        running = true
+        while (running) {
+            try {
+                Thread.sleep(1)
+                update()
+            }
+            catch(e: InterruptedException) {
+                return
+            }
+        }
+    }
+
+    private fun update() {
+        val t1 = (System.nanoTime() - start) / 1.0e9
+        val v1 = func(t1)
+        val rect = (t1 - t0) * (v0 + v1) / 2.0
+        sum  += rect
+        t0 = t1
+        v0 = v1
+    }
+}
+
+fun main(args: Array<String>) {
+    val integrator = Integrator( { sin(PI * it) } )
+    Thread.sleep(2000)
+
+    integrator.setFunc( { 0.0 } )
+    Thread.sleep(500)
+
+    integrator.stop()
+    println(integrator.getOutput())
+}