/// <summary>
///
/// </summary>
/// <returns></returns>
public Expr Expr()
{
TOKEN l_token;
Expr RetValue = Term();
while (Current_Token == TOKEN.TOK_PLUS || Current_Token == TOKEN.TOK_SUB)
{
l_token = Current_Token;
Current_Token = GetToken();
Expr e1 = Expr();
RetValue = new BinaryExpr(RetValue, e1,
l_token == TOKEN.TOK_PLUS ? OPERATOR.PLUS : OPERATOR.MINUS);
}
return(RetValue);
}
/// <summary>
///
/// </summary>
public Expr Term()
{
TOKEN l_token;
Expr RetValue = Factor();
while (Current_Token == TOKEN.TOK_MUL || Current_Token == TOKEN.TOK_DIV)
{
l_token = Current_Token;
Current_Token = GetToken();
Expr e1 = Term();
RetValue = new BinaryExpr(RetValue, e1,
l_token == TOKEN.TOK_MUL ? OPERATOR.MUL : OPERATOR.DIV);
}
return(RetValue);
}
public double Visit(BinaryExpr bin)
{
if (bin.OP == OPERATOR.PLUS)
{
return(bin.Left.accept(this) + bin.Right.accept(this));
}
else if (bin.OP == OPERATOR.MUL)
{
return(bin.Left.accept(this) * bin.Right.accept(this));
}
else if (bin.OP == OPERATOR.DIV)
{
return(bin.Left.accept(this) / bin.Right.accept(this));
}
else if (bin.OP == OPERATOR.MINUS)
{
return(bin.Left.accept(this) - bin.Right.accept(this));
}
return(Double.NaN);
}
public double Visit(BinaryExpr bin)
{
bin.Left.accept(this);
bin.Right.accept(this);
if (bin.OP == OPERATOR.PLUS)
{
eval_stack.Push(eval_stack.Pop() + eval_stack.Pop());
}
else if (bin.OP == OPERATOR.MUL)
{
eval_stack.Push(eval_stack.Pop() * eval_stack.Pop());
}
else if (bin.OP == OPERATOR.DIV)
{
eval_stack.Push(eval_stack.Pop() / eval_stack.Pop());
}
else if (bin.OP == OPERATOR.MINUS)
{
eval_stack.Push(eval_stack.Pop() - eval_stack.Pop());
}
return(Double.NaN);
}
public double Visit(BinaryExpr bin)
{
bin.Left.accept(this);
bin.Right.accept(this);
if (bin.OP == OPERATOR.PLUS)
{
Console.Write(" + ");
}
else if (bin.OP == OPERATOR.MUL)
{
Console.Write(" * ");
}
else if (bin.OP == OPERATOR.DIV)
{
Console.Write(" / ");
}
else if (bin.OP == OPERATOR.MINUS)
{
Console.Write(" - ");
}
return(Double.NaN);
}
public static Expr ParseTwo()
{
Expr r = new BinaryExpr(new Number(3), new Number(4), OPERATOR.MUL);
return(r);
}