野牛 %nonassoc 与 %token？

%token 是声明终端的基本方式。

如果存在任何优先级歧义，使用 %nonassoc 将引发语法错误。

根据我的经验，除了终端的 %token 之外，您不需要任何东西。

这是相关部分$ info bison

3.7.3 Operator Precedence
-------------------------

Use the ‘%left’, ‘%right’, ‘%nonassoc’, or ‘%precedence’ declaration to
declare a token and specify its precedence and associativity, all at
once.  These are called “precedence declarations”.  *Note Precedence::,
for general information on operator precedence.

   The syntax of a precedence declaration is nearly the same as that of
‘%token’: either

     %left SYMBOLS...

or

     %left <TYPE> SYMBOLS...

   And indeed any of these declarations serves the purposes of ‘%token’.
But in addition, they specify the associativity and relative precedence
for all the SYMBOLS:

   • The associativity of an operator OP determines how repeated uses of
     the operator nest: whether ‘X OP Y OP Z’ is parsed by grouping X
     with Y first or by grouping Y with Z first.  ‘%left’ specifies
     left-associativity (grouping X with Y first) and ‘%right’ specifies
     right-associativity (grouping Y with Z first).  ‘%nonassoc’
     specifies no associativity, which means that ‘X OP Y OP Z’ is
     considered a syntax error.

     ‘%precedence’ gives only precedence to the SYMBOLS, and defines no
     associativity at all.  Use this to define precedence only, and
     leave any potential conflict due to associativity enabled.

   • The precedence of an operator determines how it nests with other
     operators.  All the tokens declared in a single precedence
     declaration have equal precedence and nest together according to
     their associativity.  When two tokens declared in different
     precedence declarations associate, the one declared later has the
     higher precedence and is grouped first.

%token声明令牌

%nonassoc声明令牌并设置其优先级

%left/%right声明令牌并设置其优先级并设置其关联性

因此，使用哪种方法取决于您是根本不设置优先级，还是只设置优先级，或者同时设置优先级和关联性。

那么优先级和关联性有什么区别呢？它们都用于在转移令牌和减少包含具有掠夺性（以及可能的关联性）的令牌¹ 的规则之间存在冲突时解决移位/减少冲突。优先级适用于相关令牌不同（或至少具有不同的优先级）时，而关联性适用于令牌相同（或至少具有相同的优先级）时

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¹_{Yacc 实际上是将要减少的规则的优先级和关联性与要转移的令牌的优先级和关联性进行比较。只是规则总是从令牌（规则中的令牌，或用 %prec 指定的令牌）获得优先级/关联性}