The Definitive ANTLR 4 Reference

原文：https://github.com/joaoBordalo/feup-COMP/blob/master/The Definitive ANTLR 4 Reference.pdf

ANTLR V4介绍

• 新的解析技术：Adaptive LL() or ALL()
• 简化对expression的语法表达
• 自动将左递归规则重写为等价的非左递归规则
• parse-tree walker: listener and visitor pattern
• 相比v3的一些重要改进：
  • embedding actions作为高级应用，更推荐Listern和Visitor
  • 不需要设计tree grammer，使用自动生成的parse tree and tree walker
  • ALL() better than LL()

ANTLR v4 is the result of a minor detour (twenty-five years) I took in graduate
school. I guess I’m going to have to change my motto slightly.
Why program by hand in five days what you can spend twenty-five years of your
life automating?
ANTLR v4 is exactly what I want in a parser generator, so I can finally get
back to the problem I was originally trying to solve in the 1980s. Now, if I
could just remember what that was.

Chapter 1. Meet ANTLR

• StringTemplate Engine: https://www.stringtemplate.org/about.html

Chapter 2. The Big Picture

• Language的定义：a language is a set of valid sentences, a sentence is made up of phrases, and a phrase is made up of subphrases and vocabulary symbols
• Interpreter的定义：计算或者执行sentences的程序
• Translator的定义：
• parser就像只有一个入口，一个出口，地上写有单词的迷宫
• ambiguous如何处理
• ANTLR的基本数据结构和重要类有哪些？作用是什么？
  • CharStream->Lexer->Token(TokenStream)->Parser->ParseTree
  • ParseTree: RuleNode + TerminalNode
  • ANTLR实现了很多RuleNode的子类，比如StatContext, AssignContext...
• 如何遍历ParseTree?
  • 使用ParseTreeWalker
  • Listener and Visitor
  • Listener如何工作？
    • ParseTreeListener提供enter和exit方法。使用DFS遍历parseTree时，在对应的节点会触发对enter和exit方法的调用

  • Visitor如何工作？