shift-reduce-conflict - 转移/减少与 SableCC 的冲突

Question

我第一次接触 SableCC 和语法定义。
我有以下语法(其中的一部分):

query =
           {atop} attroperator |
           {query_par} l_par query r_par |
           {query_and} [q1]:query logic_and [q2]:query  |
           {query_or} [q1]:query logic_or [q2]:query |
           {query_not} logic_not query ;

我有以下错误:

shift/reduce conflict in state [stack: PCommand TLogicNot PQuery *] on
TRPar in {
       [ PQuery = PQuery * TRPar ] (shift),
       [ PQuery = TLogicNot PQuery * ] followed by TRPar (reduce)
}

shift/reduce conflict in state [stack: PCommand TLogicNot PQuery *] on
TLogicAnd in {
       [ PQuery = PQuery * TLogicAnd PQuery ] (shift),
       [ PQuery = TLogicNot PQuery * ] followed by TLogicAnd (reduce)
}

shift/reduce conflict in state [stack: PCommand TLogicNot PQuery *] on
TLogicOr in {
       [ PQuery = PQuery * TLogicOr PQuery ] (shift),
       [ PQuery = TLogicNot PQuery * ] followed by TLogicOr (reduce)
}

我通过将 l_par 和 r_par 添加到所有替代方案来解决它们，由
方式，应该提高可读性，但有没有办法做到这一点
优雅的方式？

谢谢。

Answer 1

所以，我已经解决了这个问题。我所做的基本上是定义了三个层次的关联性。

query = 
    {query_or} query logic_or term | 
    {query_term} term ;

term =
    {term_and} term logic_and factor |
    {term_factor} factor ;

factor = 
    {atop} attroperator |
    {query_not} logic_not attroperator |
    {query_par} l_par query r_par ;

这是经典的结合性方案 +,* 带有一元运算符，例如 - where + = logic_or , * = logic_and , - = logic_not .