private static Expression ParseExpression(Tree tree, ref Token token, Token[] tokens, ref int index, char terminator)
{
var node = new Expression();
while(ParseTerms(node, tree, ref token, tokens, ref index, terminator)) { }
return node;
}
private static bool ParseTerms(Expression node, Tree tree, ref Token token, Token[] tokens, ref int index, char terminator)
{
var term = ParseTerm(tree, ref token, tokens, ref index);
node.Terms.Add(term);
if (token == null || token is Operator && token.Value.Equals(terminator.ToString(CultureInfo.InvariantCulture)))
{
return false;
}
while (IsExpressionOperator(token))
{
if (IsAlternation(token))
{
node.Operators.Add(new Alternation { Value = token.Value });
}
if (IsConcatenation(token))
{
node.Operators.Add(new Concatenation { Value = token.Value });
}
if (IsRepeat(token))
{
node.Operators.Add(new Repeat { Value = token.Value });
}
if (IsExcept(token))
{
node.Operators.Add(new Except { Value = token.Value });
}
token = NextToken(tokens, ref index);
}
return true;
}