野牛-运算符优先级 [英] Bison - operator precedence

问题描述

我对Bison中的运算符优先级和关联性有疑问.

I have a question about operator precedence and associativity in Bison.

在每个示例中，我看到的作品都类似于expr 'op' expr，例如:http://dinosaur.compilertools.net/bison/bison_8.html

In every example I see the productions are like expr 'op' expr, for example :http://dinosaur.compilertools.net/bison/bison_8.html

但是，如果我要使用野牛%left和其他关联性工具，那么我将使用如下语法:

But if I would use bison %leftand others associativity tools, and I would use grammar like:

  expr|     expr binop expr
      |     expr relop expr
      |     expr logical_op expr

和

 binop: '+' 
      | '-' 
      | '*' 
      | '/' 
      ;
 relop: EE
      | NE
      | LE
      | '<'
      | GE
      | '>'
      ;
 logical_op: AND
           | OR
           ;

会使用关联性和优先级规则吗?

would associativity and precedence rules be used?

还是我需要为每个运算符写显式expr 'op' expr?

Or do I need to write explicite expr 'op' expr for every operator?

我问，因为当我尝试使用我发布的语法时，会收到有关冲突的警告.

I am asking, because when I try to use the grammar like the one I posted I get warnings about conflicts.

但是当我手工编写类似expr '+' expr的作品时，我没有得到任何警告.

But when by hand I write productions like expr '+' expr I am not getting any warnings.

推荐答案

要使优先级规则起作用，终端本身必须出现在模棱两可的产品中.因此，您不能将终端分组为非终端，也不能保留使用优先级规则的能力.

For precedence rules to work, the terminal itself must appear in the ambiguous production. So you cannot group terminals into non-terminals and retain the ability to use precedence rules.

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