feat: update structure

cs2030s/labs/Lab7/Test3.java

@@ -0,0 +1,70 @@
+import cs2030s.fp.Immutator;
+import cs2030s.fp.Memo;
+
+public class Test3 {
+  public static void main(String[] args) {
+    CS2030STest we = new CS2030STest();
+    
+    int[] _incr = new int[]{0};
+    Immutator<Integer, Integer> incr = x -> {
+      _incr[0] += 1;
+      return x + 1;
+    };
+    int[] _dbl = new int[]{0};
+    Immutator<Integer, Integer> dbl = x -> {
+      _dbl[0] += 1;
+      return x + x;
+    };
+    
+    MemoList<Integer> nat = MemoList.generate(10, 0, incr);
+    we.expect(
+      "An initial natural number only has a single evaluated element",
+      nat.toString(),
+      "[0, ?, ?, ?, ?, ?, ?, ?, ?, ?]"
+    );
+    
+    MemoList<Integer> even = nat.map(dbl);
+    we.expect(
+      "An initial even number has no evaluated element",
+      even.toString(),
+      "[?, ?, ?, ?, ?, ?, ?, ?, ?, ?]"
+    );
+    
+    nat.indexOf(2);
+    we.expect(
+      "Looking for 2 on natural number causes 2 evaluations on increments ...",
+      _incr[0],
+      2
+    );
+    we.expect(
+      "... and causes 0 evaluations on double",
+      _dbl[0],
+      0
+    );
+    
+    even.indexOf(6);
+    we.expect(
+      "Looking for 6 on even number causes 1 more evaluation on increment ...",
+      _incr[0],
+      3
+    );
+    we.expect(
+      "... and causes 4 evaluation on double",
+      _dbl[0],
+      4
+    );
+    
+    MemoList<Integer> odd = even.map(incr);
+    odd.get(8);
+    we.expect(
+      "Retrieving index 8 on odd number causes 5 more evaluation on increment ...",
+      _incr[0],
+      9
+    );
+    we.expect(
+      "... and causes 1 more evaluation on double",
+      _dbl[0],
+      5
+    );
+  }
+}