public TupleSymbol(IEnumerable <ColumnSymbol> columns, TableSymbol relatedTable = null)
     : base("tuple")
 {
     this.Columns      = columns.ToReadOnly();
     this.RelatedTable = relatedTable;
 }
 public CommandSymbol(string name, string grammar, TableSymbol resultType)
     : base(name)
 {
     this.Grammar    = grammar;
     this.resultType = resultType;
 }