public BnfRule(Bnf bnf, ReferenceOperator symbol, Operator expression)
{
Bnf = bnf;
Symbol = symbol;
Expression = expression;
ExpressionFsm = new Fsm(ExpandReferences(expression));
}
public BnfProduction(Bnf bnf, ReferenceOperator symbol, Operator expression) : base(bnf, symbol, expression)
{
}