LaTeX检查器探讨

hbghlyj

github.com/lark-parser/lark/blob/master/docs/ … part-1---the-grammar 使用Extended Backus-Naur Form (EBNF)来描述上下文无关文法 Context-Free Grammars (CFG)
ENBF定义了符号串生成非终止符的规则。
用Lark解析器创建一个LatexValidator类来验证LaTeX语法

1. from lark import Lark,Visitor
2. latex_grammar = r"""
3.     start: (command | environment | inline_math | display_math | text | escaped_character)*
4.     command: "\\" /[a-zA-Z]+/ ("[" math_content "]")? ("{" math_content "}")*
5.     environment: "\\begin" "{" env "}" math_content* "\\end" "{" env "}"
6.     env: /[a-zA-Z]+\*?/
7.     inline_math: "$" math_content "$" | "\\(" math_content "\\)"
8.     display_math: "$$" math_content "$$" | "\\[" math_content "\\]"
9.     math_content: (command | environment | text | escaped_character)*
10.     text: /[^ \t\f\r\n$\\]+/
11.     escaped_character: "\\" /[$\\,;]/
13.     %ignore /[ \t\f\r\n]+/
14. """
16. class EnvChecker(Visitor):
17.     def environment(self, node):
18.         begin_env = node.children[0].children[0].value  # \begin{env}
19.         end_env = node.children[-1].children[0].value   # \end{env}
20.         if begin_env != end_env:
21.             raise ValueError(f"Mismatched environments: {begin_env} vs {end_env}")
23. class LatexValidator:
24.     def __init__(self):
25.         self.parser = Lark(latex_grammar, parser="lalr", debug=True)
27.     def validate(self, content):
28.         tree = self.parser.parse(content)
29.         print(tree.pretty())  # Print the result tree
30.         EnvChecker().visit(tree)
31.         return True

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hbghlyj

测试：

1. LatexValidator = LatexValidator()
2. LatexValidator.validate(r"""\begin{document}
3. \begin{equation}
4.     E = mc^2
5. \end{equation}
6. \begin{equation*}
7.     F = ma
8. \end{equation*}
9. \end{document}
10. """)

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输出：
start
  environment
    env document
    math_content
      environment
        env     equation
        math_content
          text  E
          text  =
          text  mc^2
        env     equation
      environment
        env     equation*
        math_content
          text  F
          text  =
          text  ma
        env     equation*
    env document

hbghlyj

测试：

1. LatexValidator = LatexValidator()
2. LatexValidator.validate(r"""\begin{document}
3. \begin{equation}
4.     E = mc^2
5. \end{equation}
6. \begin{equation*}
7.     F = ma
8. \end{equation}
9. \end{document}
10. """)

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输出：ValueError: Mismatched environments: equation* vs equation