feat: update structure

cs2030s/labs/Lab7/Test1.java

@@ -0,0 +1,50 @@
+import cs2030s.fp.Immutator;
+import cs2030s.fp.Memo;
+
+public class Test1 {
+  public static void main(String[] args) {
+    CS2030STest we = new CS2030STest();
+    
+    int[] eval = new int[]{0};
+    Immutator<Integer, Integer> incr = x -> {
+      eval[0] += 1;
+      return x + 1;
+    };
+    
+    MemoList<Integer> l = MemoList.generate(4, 0, incr);
+    
+    we.expect(
+      "An initial MemoList only has a single evaluated element",
+      l.toString(),
+      "[0, ?, ?, ?]"
+    );
+    
+    l.indexOf(2);
+    we.expect(
+      "Looking for 2 causes 2 evaluations",
+      eval[0],
+      2
+    );
+    
+    l.indexOf(1);
+    we.expect(
+      "Looking for 1 does not need any more evaluation",
+      eval[0],
+      2
+    );
+    
+    l.get(1);
+    we.expect(
+      "Retrieving index 1 does not need any more evaluation",
+      eval[0],
+      2
+    );
+    
+    l.get(3);
+    we.expect(
+      "Retrieving index 3 causes one more evaluation",
+      eval[0],
+      3
+    );
+  }
+}