C# LL(1) 句法分析器：SELECT 集计算函数

private Dictionary<string, List<string>> GetSelect(Dictionary<string, List<string>> production1, Dictionary<string, List<string>> firsts1, Dictionary<string, List<string>> follows1)
{
    // 初始化 SELECT 集
    Dictionary<string, List<string>> selects1 = new Dictionary<string, List<string>>();
    foreach (var item in production1)
        selects1.Add(item.Key, new List<string>());

    // 遍历每个产生式，计算对应的 SELECT 集
    foreach (var nonterm in production1.Keys)
    {
        foreach (var prod in production1[nonterm])
        {
            List<string> select = new List<string>();
            bool flag = true;
            // 对于产生式中的每个符号，计算其 FIRST 集
            foreach (var s in prod)
            {
                if (IsTerminal(s))
                {
                    select.Add(s.ToString());
                    flag = false;
                    break;
                }
                else
                {
                    foreach (var f in firsts1[s])
                    {
                        if (!f.Equals("#") && !select.Contains(f))
                            select.Add(f);
                    }
                    if (!IsReachEmpty(s, production1))
                    {
                        flag = false;
                        break;
                    }
                }
            }
            // 如果产生式中所有符号的 FIRST 集都包含空串，则将 FOLLOW 集加入 SELECT 集中
            if (flag)
            {
                foreach (var f in follows1[nonterm])
                {
                    if (!select.Contains(f))
                        select.Add(f);
                }
            }
            selects1[nonterm].Add(string.Join("", select.ToArray()));
        }
    }
    return selects1;
}