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转移/减少与SableCC的冲突

sablecc shift-reduce-conflict

2

dierre · 技术社区 · 14 年前

我有以下语法(它的一部分):

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 ;

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)
}

我通过在所有备选方案中加上l\u par和r\u par来解决它们方法,应该增加可读性,但有没有一种方法可以做到这一点优雅的举止?

谢谢。

1 回复 | 直到 14 年前

1

3

dierre 14 年前

所以,我解决了这个问题。我所做的基本上是定义三个层次的关联性。

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+,*和一元运算符,如-where + = logic_or , * = logic_and , - = logic_not .