Initial data commit

Task/Delegates/Wren/delegates.wren

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+class Thingable {
+    thing { }
+}
+
+// Delegate that doesn't implement Thingable
+class Delegate {
+    construct new() { }
+}
+
+// Delegate that implements Thingable
+class Delegate2 is Thingable {
+    construct new() { }
+
+    thing { "delegate implementation" }
+}
+
+class Delegator {
+    construct new() {
+        _delegate = null
+    }
+
+    delegate     { _delegate }
+    delegate=(d) { _delegate = d }
+
+    operation {
+        if (!_delegate || !(_delegate is Thingable)) return "default implementation"
+        return _delegate.thing
+    }
+}
+
+// without a delegate
+var d = Delegator.new()
+System.print(d.operation)
+
+// with a delegate that doesn't implement Thingable
+d.delegate = Delegate.new()
+System.print(d.operation)
+
+// with a delegate that does implement Thingable
+d.delegate = Delegate2.new()
+System.print(d.operation)