public override Expression Evaluate(EvalStore store)
{
Table data = store.Get<Table>("$DATA");
int col = -1;
if (data != null) {
col = data.ColumnDefinitions.IndexOf(this.Name);
}
Element e = null;
if (col >= 0) {
List<int> group = store.Get<List<int>>("$GROUP");
if (group != null) {
Element[] values = new Element[group.Count];
int i=0;
foreach (int row in group) {
values[i++]= data[row, col];
}
e = new Element(values);
}
else {
Element[] row = store.Get<Element[]>("$ROW");
e = row[col];
}
}
else {
if (store.Exists(this.Name)) {
e = store.Get<Element>(this.Name);
}
else {
EvalContext ctx = store.Get<EvalContext>("$EVAL_CONTEXT");
if (ctx == null || ctx.Context != EvalContext.ContextType.SELECT) {
if (!this.Name.Contains(" ")) {
e = new Element(this.Name);
}
}
}
}
if (e != null) {
return new ConstExpr(e);
}
else {
throw new Exception("No such column: " + this.Name);
}
}