^和！是什么?在ANTLR语法中代表 [英] What does ^ and ! stand for in ANTLR grammar

问题描述

我很难弄清楚^和！是什么.代表ANTLR语法术语.

I was having difficulty figuring out what does ^ and ! stand for in ANTLR grammar terminology.

推荐答案

看看 ANTLR速查表:

!不在AST中
^创建AST根节点

! don't include in AST
^ make AST root node

和^也可以用于重写规则:... -> ^( ... ).例如，以下两个解析器规则是等效的:

And ^ can also be used in rewrite rules: ... -> ^( ... ). For example, the following two parser rules are equivalent:

expression
  :  A '+'^ A ';'!
  ;

和:

expression
  :  A '+' A ';' -> ^('+' A A)
  ;

两者都创建以下AST:

Both create the following AST:

  +
 / \
A   A

换句话说:+是根节点，两个A是其子节点，而;从树中省略了.

In other words: the + is made as root, the two A's its children, and the ; is omitted from the tree.

这篇关于^和！是什么?在ANTLR语法中代表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！