public static void Main()
{
var e1 = new Add(new CstI(17), new Var("z")); // => Add(17, z)
// WriteLine automatically calls .ToString on objects passed to it
Console.WriteLine(e1);
// (ii) Create three more expressions and print them
// Easter egg: I totally stole them from Intro2.fs
var e2 = new CstI(17); // => 17
var e3 = new Add(new CstI(3), new Var("a")); // => Add(3, a)
var e4 = new Add(new Mul(new Var("b"), new CstI(9)), new Var("a"));
// => Add(Mul(b, 9), a)
Console.WriteLine(string.Format("{0}\n{1}\n{2}", e2, e3, e4));
// (iii) Add the eval function to each subclass of `Expr`
var env = new Dictionary <string, int> {
{ "x", 5 },
{ "y", 42 }
};
var e5 = new Add(new Var("x"), new CstI(5));
Console.WriteLine(e5.Eval(env)); // => 10
// (iv) Add the simplify function to each subclass of `Expr`
var e6 = new Add(new Var("x"), new CstI(0)); // => x
var e7 = new Sub(new Var("x"), new CstI(0)); // => x
var e8 = new Mul(new CstI(5), new CstI(0)); // => 0
var e9 = new Mul(new Var("x"), new CstI(1)); // => x
Console.WriteLine(string.Format("{0}\n{1}\n{2}\n{3}",
e6.Simplify(), e7.Simplify(), e8.Simplify(), e9.Simplify()));
}