added assignment 7 ex 3

src/Assignment7/Ex3.sc

@@ -0,0 +1,12 @@
+def addStream(s1: LazyList[Int], s2: LazyList[Int]): LazyList[Int] = {
+  s1 zip s2 map (p => p._1 + p._2)
+}
+
+def fibonacci(): LazyList[Int] = {
+  0 #:: addStream(
+    1 #:: fibonacci(),
+    fibonacci()
+  )
+}
+
+fibonacci().take(10).toList