Initial data commit

Task/Null-object/Wren/null-object.wren

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+// Declare a variable without giving it an explicit value.
+var s
+
+// We can now check for nullness in one of these ways.
+System.print(s)
+System.print(s == null)
+System.print(s is Null)
+System.print(s.type == Null)
+
+// Similarly, if we define this function without giving it a return value.
+var f = Fn.new {
+    System.print("I'm a function with no explicit return value.")
+}
+
+// And now call it.
+var g = f.call()
+// We find that the return value is null.
+System.print(g)