public Expr MatchFactor()
{
Expr left = MatchValue();
if (fallback)
{
return(null);
}
if (tk.Type == TokenType.Times)
{
var a = new Arith();
a.Op = ArithOp.Mul;
Match(TokenType.Times);
a.Left = left;
a.Right = MatchFactor();
if (fallback)
{
return(null);
}
return(a);
}
else if (tk.Type == TokenType.Slash)
{
var a = new Arith();
a.Op = ArithOp.Div;
Match(TokenType.Slash);
a.Left = left;
a.Right = MatchFactor();
if (fallback)
{
return(null);
}
return(a);
}
if (fallback)
{
return(null);
}
return(left);
}
public Expr MatchTerm()
{
Expr left = MatchFactor();
if (fallback)
{
return(null);
}
if (tk.Type == TokenType.Plus)
{
var a = new Arith();
a.Op = ArithOp.Add;
Match(TokenType.Plus);
a.Left = left;
a.Right = MatchTerm();
if (fallback)
{
return(null);
}
return(a);
}
else if (tk.Type == TokenType.Minus)
{
var a = new Arith();
a.Op = ArithOp.Sub;
Match(TokenType.Minus);
a.Left = left;
a.Right = MatchTerm();
if (fallback)
{
return(null);
}
return(a);
}
if (fallback)
{
return(null);
}
return(left);
}