private static void ReduceTermsForCommutativeOperator(List <object> tokens, BinaryOperator op)
{
Debug.Assert(tokens.IndexOf(null) == -1, "The tokens array contains a null.");
int index = tokens.IndexOf(op);
while (index != -1)
{
Debug.Assert(index != 0 && index != tokens.Count - 1, "index != 0 && index != tokens.Count - 1");
var terms = new List <IExpression>();
int endIndex = AddOperands(tokens, op, terms, index - 1);
Debug.Assert(endIndex > index, "endIndex > index");
// Replace all the tokens from the start index to the end index with a CommutativeExpression.
var commutative = new CommutativeExpression(op, terms);
tokens[index - 1] = commutative.Simplify();
tokens.RemoveRange(index, endIndex - index + 1);
if (index == tokens.Count)
{
break;
}
index = tokens.IndexOf(op, index + 1);
}
}
private static bool TrySplitSubExpressions(IExpression expression, ref string allWords,
ref string exactPhrase, ref string anyWord, ref string withoutWords)
{
var commutative = expression as CommutativeExpression;
if (commutative == null || commutative.Operator != BinaryOperator.And)
{
return(false);
}
// We have some ANDed sub-expressions. See if we can still split them.
UnaryExpression not = null;
var andedLiterals = new List <IExpression>();
LiteralTerm exact = null;
CommutativeExpression oredLiterals = null;
foreach (IExpression commTerm in commutative.Terms)
{
IExpression term = commTerm;
// Is it a literal?
var literal = term as LiteralTerm;
if (literal != null)
{
if (exact == null && literal.IsExact)
{
exact = literal;
}
else
{
andedLiterals.Add(literal);
}
continue;
}
// Is it a NOT?
var unary = term as UnaryExpression;
if (unary != null)
{
if (not != null || unary.Operator != UnaryOperator.Not)
{
return(false); // More than one NOT or something other than NOT - cannot be split.
}
if (unary.Term is LiteralTerm || (unary.Term is CommutativeExpression &&
((CommutativeExpression)unary.Term).Operator == BinaryOperator.Or))
{
not = unary;
continue;
}
return(false);
}
var innerAndOr = term as CommutativeExpression;
if (innerAndOr != null)
{
if (innerAndOr.Operator != BinaryOperator.Or || !AreAllLiterals(innerAndOr.Terms))
{
return(false); // A sub-expression - cannot be split.
}
if (oredLiterals != null)
{
return(false); // More than one OR - cannot be split.
}
oredLiterals = innerAndOr;
continue;
}
return(false);
}
if (andedLiterals.Count > 0)
{
allWords = andedLiterals.Count == 1 ? andedLiterals[0].GetUserExpression() : JoinLiterals(andedLiterals);
}
if (not != null)
{
if (not.Term is LiteralTerm)
{
withoutWords = not.Term.GetUserExpression();
}
else
{
Debug.Assert(not.Term is CommutativeExpression, "not.Term is CommutativeExpression");
withoutWords = JoinLiterals(((CommutativeExpression)not.Term).Terms);
}
}
if (exact != null)
{
exactPhrase = exact.Value.Trim(LiteralTerm.Quote);
}
if (oredLiterals != null)
{
anyWord = JoinLiterals(oredLiterals.Terms);
}
return(true);
}