Initial data commit

Task/Active-object/F-Sharp/active-object.fs

@@ -0,0 +1,43 @@
+open System
+open System.Threading
+
+// current time in seconds
+let now() = float( DateTime.Now.Ticks / 10000L ) / 1000.0
+
+type Integrator( intervalMs ) as x =
+  let mutable k = fun _ -> 0.0  // function to integrate
+  let mutable s = 0.0           // current value
+  let mutable t0 = now()        // last time s was updated
+  let mutable running = true    // still running?
+
+  do x.ScheduleNextUpdate()
+
+  member x.Input(f) = k <- f
+
+  member x.Output() = s
+
+  member x.Stop() = running <- false
+
+  member private x.Update() =
+    let t1 = now()
+    s <- s + (k t0 + k t1) * (t1 - t0) / 2.0
+    t0 <- t1
+    x.ScheduleNextUpdate()
+
+  member private x.ScheduleNextUpdate() =
+    if running then
+      async { do! Async.Sleep( intervalMs )
+              x.Update()
+            }
+      |> Async.Start
+
+let i = new Integrator(10)
+
+i.Input( fun t -> Math.Sin (2.0 * Math.PI * 0.5 * t) )
+Thread.Sleep(2000)
+
+i.Input( fun _ -> 0.0 )
+Thread.Sleep(500)
+
+printfn "%f" (i.Output())
+i.Stop()