addCol method
Add column and return builder for column metadata. Columns cannot be added after adding the first row.
Implementation
HDictBuilder addCol(String name, {HVal Function()? fill}) {
if (!HDict.isTagName(name)) {
throw ArgumentError("Invalid column name: $name");
}
BCol col = BCol(name);
_cols.add(col);
if (fill != null) {
_rows.forEach((row) => row.add(fill()));
} else {
_rows.forEach((row) => row.add(null));
}
return col.meta;
}