static void Main()
{
// Create your expression here
Expression expr = new PlusExpression(
left: new ConstantExpression(4),
right: new MinusExpression(
left: new ConstantExpression(1),
right: new ConstantExpression(2)));
// Example:
//Expression expr = new PlusExpression(
// new ConstantExpression(4),
// new PlusExpression(
// new ConstantExpression(1),
// new ConstantExpression(2)));
// We print the textual representation
Console.Write(expr.ToString());
Console.Write(" = ");
// ... and then the result of evaluating
Console.WriteLine(expr.Evaluate());
Console.ReadKey();
}