public override IResultValue Evaluate()
{
IResultValue list = List.Evaluate();
IResultValue index = Index.Evaluate();
if (index.Type != MathType.Integer)
{
throw new EvaluationException(this, "Ordinal index must be integer.");
}
if (list.Type != MathType.List)
{
throw new EvaluationException(this, "Ordinal access can only be used on a list.");
}
return(new ResultNumberReal(list.ToList()[(int)index.ToInteger()]));
}