private Filter <T> Combine(Filter <T> right, Filter <T> top)
{
if (right == null)
{
return(top);
}
if (top == null)
{
return(right);
}
if (right is FilterKeyword <T> )
{
FilterKeyword <T> keyword = (FilterKeyword <T>)right;
if (top is FilterKeyword <T> )
{
// easy case, we are parsing a string of words, so combine them back into a single literal to match.
FilterKeyword <T> keyword2 = (FilterKeyword <T>)top;
keyword.Keyword = new FilterLiteral(keyword.Keyword.Literal + " " + keyword2.Keyword.Literal);
return(right);
}
}
// everything else is some sort of parse error, so this is error recover code...
return(right);
}
private Filter <T> Reduce(QuickFilterToken token)
{
while (stack.Count > 0)
{
Filter <T> top = stack.Pop();
if (stack.Count == 0)
{
return(top);
}
Filter <T> op = stack.Peek();
if (token > op.Precidence)
{
return(top);
}
op = stack.Pop();
// now combine "top" and "op"
if (op is FilterKeyword <T> )
{
FilterKeyword <T> keyword = (FilterKeyword <T>)op;
op = Combine(keyword, top);
}
else if (op is FilterAnd <T> )
{
FilterAnd <T> and = (FilterAnd <T>)op;
and.Right = Combine(and.Right, top);
}
else if (op is FilterOr <T> )
{
FilterOr <T> or = (FilterOr <T>)op;
or.Right = Combine(or.Right, top);
}
else if (op is FilterNot <T> )
{
FilterNot <T> not = (FilterNot <T>)op;
not.Right = Combine(not.Right, top);
}
else if (op is FilterParens <T> )
{
FilterParens <T> parens = (FilterParens <T>)op;
parens.Expression = Combine(parens.Expression, top);
}
stack.Push(op);
}
return(null);
}
