feat: update structure

cs2030s/labs/Lab6/Bool.java

@@ -0,0 +1,25 @@
+import cs2030s.fp.Constant;
+import cs2030s.fp.Memo;
+
+class Bool implements Cond {
+  private Memo<Boolean> val;
+
+  public Bool(Constant<Boolean> val) {
+    this.val = Memo.from(val);
+  }
+
+  @Override
+  public boolean eval() {
+    return this.val.get();
+  }
+
+  @Override
+  public String toString() {
+    return this.val.toString().substring(0, 1);
+  }
+
+  @Override
+  public Cond neg() {
+    return new Not(this);
+  }
+}