private ExpressionTreeNode ParseNot()
{
if (_tokenReader.Token != Token.Not)
{
return(ParseTerm());
}
_tokenReader.NextToken();
var term = ParseNot();
return(ExpressionTreeNode.CreateNot(term));
}
/// <summary>
/// AND(NOT,NOT) -> NOT(OR)
/// </summary>
/// <param name="node"></param>
private static ExpressionTreeNode TwoNotInAndRule(ExpressionTreeNode node, ref int count)
{
if (node == null)
{
return(null);
}
if (node.Operation == "AND" && node.Child1.Operation == "NOT" && node.Child2.Operation == "NOT")
{
var andChild = ExpressionTreeNode.CreateOr(node.Child1.Child1, node.Child2.Child1);
node = ExpressionTreeNode.CreateNot(andChild);
count++;
}
return(node);
}
/// <summary>
/// OR(NOT, NOT) -> ALL - if terms are not equal
/// OR(NOT, NOT) -> NOT(term) - if terms are equal
/// </summary>
/// <param name="node"></param>
private static ExpressionTreeNode TwoNotInOrRule(ExpressionTreeNode node, ref int count)
{
if (node == null)
{
return(null);
}
if (node.Operation == "OR" && node.Child1.Operation == "NOT" && node.Child2.Operation == "NOT")
{
if (node.Child1.Child1.Term == node.Child2.Child1.Term)
{
node = ExpressionTreeNode.CreateNot(node.Child1.Child1);
}
else
{
node = ExpressionTreeNode.CreateAllNode();
}
count++;
}
return(node);
}