static void Main(string[] args)
{
// Abstract Syntax Tree (AST) for 5*10
Exp e = new BinaryExp(new NumericConstant(5),
new NumericConstant(10),
OPERATOR.MUL);
//
// Evaluate the Expression
//
//
Console.WriteLine(e.Evaluate(null));
// AST for -(10 + (30 + 50 ) )
e = new UnaryExp(
new BinaryExp(new NumericConstant(10),
new BinaryExp(new NumericConstant(30),
new NumericConstant(50),
OPERATOR.PLUS),
OPERATOR.PLUS),
OPERATOR.MINUS);
//
// Evaluate the Expression
//
Console.WriteLine(e.Evaluate(null));
//
// Pause for a key stroke
//
Console.Read();
}
/// <summary>
///
/// </summary>
public Exp Factor()
{
TOKEN l_token;
Exp RetValue = null;
if (Current_Token == TOKEN.TOK_DOUBLE)
{
RetValue = new NumericConstant(GetNumber());
Current_Token = GetToken();
}
else if (Current_Token == TOKEN.TOK_OPAREN)
{
Current_Token = GetToken();
RetValue = Expr(); // Recurse
if (Current_Token != TOKEN.TOK_CPAREN)
{
Console.WriteLine("Missing Closing Parenthesis\n");
throw new Exception();
}
Current_Token = GetToken();
}
else if (Current_Token == TOKEN.TOK_PLUS || Current_Token == TOKEN.TOK_SUB)
{
l_token = Current_Token;
Current_Token = GetToken();
RetValue = Factor();
RetValue = new UnaryExp(RetValue,
l_token == TOKEN.TOK_PLUS ? OPERATOR.PLUS : OPERATOR.MINUS);
}
else
{
Console.WriteLine("Illegal Token");
throw new Exception();
}
return(RetValue);
}
