此语法是否通过右递归定义右结合性

Question

我正在阅读 this article 关于将 ** 运算符添加到 EcmaScript 规范的内容，其中作者声明如下：

Exponentiation must be evaluated before multiplication and more importantly, the BNF grammar must be written such that the operator’s right-associativity is clearly defined (unlike MultiplicativeExpression, which is left-associative).

而他在文法中定义新的非终结符号ExponentiationExpression为：

ExponentiationExpression : 
  UnaryExpression[?Yield]
  UnaryExpression[?Yield] ** ExponentiationExpression[?Yield]

MultiplicativeExpression[Yield] :
  ExponentiationExpression[?Yield]
  MultiplicativeExpression[?Yield] MultiplicativeOperator ExponentiationExpression[?Yield]

This article 表示：

To write a grammar that correctly expresses operator associativity:

For left associativity, use left recursion.

For right associativity, use right recursion.

他似乎遵循了该规则并通过使用 右递归 在这里为 ExponentiationExpression 定义了关联性：

ExponentiationExpression -> UnaryExpression[?Yield] ** ExponentiationExpression[?Yield]

我说得对吗？

Answer 1

Am I right?

是.

此语法是否通过右递归定义右结合性

Does this grammar define right-associativity by right recursion

javascript

compiler-construction

context-free-grammar

ecmascript-6