/// <summary>
/// Parses an order term.
/// Expression (ASC|DESC)?, (Expression (ASC|DESC)?)*
/// </summary>
/// <returns> An oder term node. </returns>
private static Node ParseOrderTerm(ref int position, List <Token> tokens)
{
OrderTermNode orderTermNode = new OrderTermNode();
// Expression
var expression = ParseExpressionNode(ref position, tokens);
if (expression == null)
{
ThrowError("Order by parser", "Expected expression.", position, tokens);
}
else
{
orderTermNode.AddExpression(expression);
}
// ASC|DESC
orderTermNode.SetIsAscending(ParseAscDesc(ref position, tokens));
// Comma singnals another order term.
if (CheckToken(position, Token.TokenType.Comma, tokens))
{
position++;
orderTermNode.AddNext(ParseOrderTerm(ref position, tokens));
}
return(orderTermNode);
}
/// <summary>
/// Expects an expression node and possibly next order term node.
/// </summary>
public void Visit(OrderTermNode node)
{
if (node.exp == null)
{
throw new ArgumentNullException($"{this.GetType()}, failed access expression.");
}
else
{
node.exp.Accept(this);
}
this.result.Add(ExpressionComparer.Factory(this.expressionHolder, node.isAscending, false));
if (node.next != null)
{
node.next.Accept(this);
}
}
public void Visit(OrderTermNode node)
{
throw new NotImplementedException();
}
