/// <summary>
/// Parses a group by term.
/// Expression (, Expression)*
/// </summary>
/// <returns> A group by term node. </returns>
private static Node ParseGroupByTerm(ref int position, List <Token> tokens)
{
GroupByTermNode groupByTermNode = new GroupByTermNode();
// Expression
var expression = ParseExpressionNode(ref position, tokens);
if (expression == null)
{
ThrowError("Group by parser", "Expected expression.", position, tokens);
}
else
{
groupByTermNode.AddExpression(expression);
}
// Comma signals another group term.
if (CheckToken(position, Token.TokenType.Comma, tokens))
{
position++;
groupByTermNode.AddNext(ParseGroupByTerm(ref position, tokens));
}
return(groupByTermNode);
}
/// <summary>
/// Expects an expression and possibly the next group by term.
/// </summary>
public void Visit(GroupByTermNode node)
{
if (node.exp == null)
{
throw new ArgumentNullException($"{this.GetType()}, failed to access expression.");
}
else
{
node.exp.Accept(this);
}
if (node.next != null)
{
node.next.Accept(this);
}
}
public void Visit(GroupByTermNode node)
{
throw new NotImplementedException();
}