antlr | 易学教程

基于ANTLR语法树编写解释引擎最佳实践

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> Tiny模板引擎的实现方式原来是采用的编译方式，最近发生了一些问题，因此我觉得有必要把编译方式调整为解释方式，为此就开始了此次实现活动。编译方式存在的问题当时采用编译方式，主要是考虑到编译方式在运行时不必再去遍历语法树，因此就采用了编译方式。但是在实际应用当中，出现了如下问题：文件路径冲突的问题由于采用的是编译方式，这个时候就存在在一个选择，即：Java源代码落地或不落地的选择。如果Java文件不落地，则在有问题的时候，如果想要进行代码调试（虽然这种场景并不多见），那么就没有源代码可供调试。如果Java代码落地，则会存在一个问题，那就是资源文件在磁盘文件中产生冲突的问题。同样的问题对于class文件也存在，如果不落地，那么每次应用重启动的时候，都要重新编译这些文件以产生class文件；如果落地，则也会产生冲突的问题。当然，Tiny模板引擎通过增加一个配置项，解决了这个冲突的问题，但是由于增加了一个配置项，从客观上增加了维护人员的工作量，也容易造成当维护人员不了解这里面的道道，忘记设置从而导致在一台服务器中部署多个Tiny应用时多个应用中的模板文件生成的java文件和class文件的冲突，从而导致出现问题。 PermSize内存占用问题采用编译方式的时候，由于每个模板文件都要生成一个类

为什么 antlr 用于模板引擎不是个好主意

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 我在发布 jfinal 3.0 的时候认为 antlr 用于 "模板引擎" 并不是个好主意，两年多时间过去了，我的观点更进一步：认为 antlr 在多数 “非模板引擎” 的场景下使用也不是个好主意。在发布 jfinal 3.0 的时候谈到 antlr，只言片语信息量太少，引起了部分人的误解，今天就来稍稍展开聊一聊。一、antlr 生成 Parser 难于调试、难于阅读首先现场直观来感受一下 jfinal 手写 Parser 与使用 antlr 生成的 parser 的对比，下面是为 jfinal enjoy 模板引擎手写的 parser： https://gitee.com/jfinal/jfinal/blob/master/src/main/java/com/jfinal/template/stat/Parser.java 空行 + 注释 + java 代码一共 278 行，干净利落，人类轻松阅读。更重要的是其用到的 Recursive Descent 算法简洁可靠，功能强大，随手可得。了解这个算法原理的同学几个小时就可以手撸一个自己的 Parser 出来。再来看一下 antlr 为模板引擎生成的 parse： https://gitee.com/xiandafu/beetl/blob/master

Switching to island mode on multi-character token

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问题 I am working on a grammar that is basically an island grammar. Let's say the "island" is everything between braces, the "sea" is everything that is not. Like this: { (island content) } Then this simple grammar works: IslandStart : '{' -> pushMode(Island) ; Fluff : ~[\{\}]+ ; .... But I'm having trouble to come up with a similar solution to a case where I want the complex (multi-character) opening for my "island" block, like this: {# (island content) } In this case I don't know how to make a

When rewriting tree on ANTLR, java.lang.NullPointerException is thrown

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问题 I'm trying to create a parser for QuickBasic and this is my attempt to get the comments: grammar QuickBasic; options { language = 'CSharp2'; output = AST; } tokens { COMMENT; } parse : .* EOF ; // DOESN'T WORK Comment : R E M t=~('\n')* { Text = $t; } -> ^(COMMENT $t) | Quote t=~('\n')* { Text = $t; } -> ^(COMMENT $t) ; Space : (' ' | '\t' | '\r' | '\n' | '\u000C') { Skip(); } ; fragment Quote : '\''; fragment E : 'E' | 'e'; fragment M : 'M' | 'm'; fragment R : 'R' | 'r'; Even if I rewrite

Looking for Antlr 3 / C sample main()

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问题 I see a few sample main() for C floating about, e.g. http://www.antlr.org/wiki/display/ANTLR3/Five+minute+introduction+to+ANTLR+3 and http://www.antlr.org/api/C/index.html The dereference seems to be AST. I don't know what that is , and - please excuse me - don't want to if I can avoid it. I woudl like to just define the lexer & grammar (for modem AT commands) and have the main() auto-generated, or cut/pasted from somewhere. Ons slight twist is that most examples seem to read from a file,

Modify expressions, generated by Antlr?

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问题 I would like to read expressions with Antlr4 and the perform some modifications on them. For example, if grammar is arithmetic, I would modify expression, representing 2 * (3 + 1) with 2 * 4 and then with 8 This is "calculation" or "simplification". To perform this thing I would create some tree structure and the first idea is to use the very same trees, created by Antlr. Unfortunately, I don't see any setters for children. How to accomplish? Should I really duplicate Antlr trees with my own

Antlr and PL/I grammar

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问题 Right now we would like to have the grammar of PL/I, COBOL based on Antlr4. Is there anyone provide these grammars If not, can you please share your thought/experience on developing these grammars from scratch Thanks 回答1: I assume you mean IBM PL/I and COBOL. (Not many other PL/Is around, but I don't think that really changes the answer much). The obvious place to look for mature ANTLR grammars is ANTLR3 grammar library; no PL/1 or COBOL grammars there. The Antlr V4 (a very new, radical,

Antlr and PL/I grammar

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Status of Javascript in antlr 3.4 or 3.5 [closed]

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问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 5 years ago . What is the status of the JavaScript target in ANTLR 3.4 or 3.5? I have been looking online for an answer to this question but so far I have found nothing. I know that it was broken in v3.2 and then it was fixed in v3.3, but it's not listed in the ANTLR 3.4 release notes as a

回波总

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 波总好, 在谈谈我对 JFinal Marketing 的一些看法那篇博文的评论中我们谈论到了 ANTLR, 这里继续和波总谈谈在技术上我对这方面的理解. 先说下 ANTLR 到底什么. ANTLR 官网给自己的定义是: ANTLR (ANother Tool for Language Recognition) is a powerful parser generator for reading, processing, executing, or translating structured text or binary files. It's widely used to build languages, tools, and frameworks. From a grammar, ANTLR generates a parser that can build and walk parse trees. 简单地说 ANTLR 是一个词法语法分析工具, 它不是一个应用层面的库, 也不是为应用程序开发使用的. ANTLR 的用户是需要定义某种语法, 并实现对该语法文件的解析的库开发者. 对 ANTLR 的应用场景在这篇文章中有更多的介绍. 下面列举几个使用 ANTLR 的项目: Groovy - 解析