bison/flex中的简单XML解析器

问题描述

我想使用bison/flex创建简单xml解析器.我不需要验证，注释，参数，只需<tag>value</tag>，其中 value 可以是数字，字符串或其他<tag>value</tag>.

I would like to create simple xml parser using bison/flex. I don't need validation, comments, arguments, only <tag>value</tag>, where value can be number, string or other <tag>value</tag>.

例如:

<div>
  <mul>
    <num>20</num>
    <add>
      <num>1</num>
      <num>5</num>
    </add>
  </mul>
  <id>test</id>
</div>

如果有帮助，我知道可能会出现的所有标签的名称.我知道给定标签可以容纳多少个子标签.是否有可能创建像这样的野牛解析器:

If it helps, I know the names of all tags that may occur. I know how many sub-tag can be hold by given tag. Is it possible to create bison parser that would do something like that:

- new Tag("num", 1)           // tag1
- new Tag("num", 5)           // tag2
- new Tag("add", tag1, tag2)  // tag3
- new Tag("num", 20)          // tag4
- new Tag("mul", tag4, tag3)
...
- root = top_tag

标记&子标签数量:

Tag & number of sub-tags:

• 数字:1(仅值)
• str:1(仅值)
• 添加|子| mul | div:2(num | str |标签，num | str |标签)

您能否帮助我进行语法设计，以便像上面给出的那样创建AST?

Could you help me with grammar to be able to create AST like given above?

推荐答案

对于您的要求，我认为 yax系统会很好.在自述文件中:

For your requirements, I think the yax system would work well.From the README:

yax项目的目标是允许使用YACC(实际上是Gnu Bison)来解析/处理XML文档.

The goal of the yax project is to allow the use of YACC (Gnu Bison actually) to parse/process XML documents.

实现上述目标的关键软件是提供一个可以从XML文档生成XML词法标记流的库.

The key piece of software for achieving the above goal is to provide a library that can produce an XML lexical token stream from an XML document.

可以包装此流以创建yylex()实例，以将令牌提供给Bison语法以解析和处理XML文档.

This stream can be wrapped to create an instance of yylex() to feed tokens to a Bison grammar to parse and process the XML document.

使用流和Bison语法，可以至少进行以下类型的活动.

Using the stream plus a Bison grammar, it is possible to carry at least the following kinds of activities.

1. 验证XML文档，
2. 直接解析XML文档以创建内部数据结构，
3. 构造DOM树.

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