public TestClass() { Expr e = new Add(new CstI(17), new Var("z")); Console.WriteLine(e); // (ii) Expr e1 = new Mul(new CstI(100), e); Console.WriteLine(e1); Expr e2 = new Sub(e1, e); Console.WriteLine(e2); Expr e3 = new Add(e1, e2); Console.WriteLine(e3); }