解析不完整的语法 [英] Parsing with incomplete grammars

问题描述

有什么通用的解决方案如何使用不完整的语法?就我而言，我只想检测Delphi(Pascal)文件中的方法，这意味着procedures和functions.以下第一次尝试有效

Are there any common solutions how to use incomplete grammars? In my case I just want to detect methods in Delphi (Pascal)-files, that means procedures and functions. The following first attempt is working

    methods
      : ( procedure | function | . )+
      ;

但这是一个解决方案吗?有更好的解决方案吗?是否可以通过某个动作停止解析(例如，在检测到implementation之后).使用预处理程序有意义吗?当是的时候-怎么办?

but is that a solution at all? Are there any better solutions? Is it possible to stop parsing with an action (e. g. after detecting implementation). Does it make sense to use a preprocessor? And when yes - how?

推荐答案

如果您只是在寻找姓名，那么就这么简单:

If you're only looking for names, then something as simple as this:

grammar PascalFuncProc;

parse
  :  (Procedure | Function)* EOF
  ;

Procedure
  :  'procedure' Spaces Identifier
  ;

Function
  :  'function' Spaces Identifier
  ;

Ignore
  :  (StrLiteral | Comment | .) {skip();}
  ;

fragment Spaces     : (' ' | '\t' | '\r' | '\n')+;
fragment Identifier : ('a'..'z' | 'A'..'Z' | '_') ('a'..'z' | 'A'..'Z' | '_' | '0'..'9')*;
fragment StrLiteral : '\'' ~'\''* '\'';
fragment Comment    : '{' ~'}'* '}';

可以解决问题.请注意，我对Delhpi/Pascal不太熟悉，因此我肯定会搞砸StrLiteral和/或Comment，但这很容易解决.

will do the trick. Note that I am not very familiar with Delhpi/Pascal, so I am surely goofing up StrLiterals and/or Comments, but that'll be easily fixed.

从上面的语法生成的词法分析器将只产生两种类型的标记(Procedure s和Function s)，其余的输入(字符串文字，注释或如果没有匹配则为单个字符): .)将立即从词法分析器中丢弃(skip()方法).

The lexer generated from the grammar above will only produce two type of tokens (Procedures and Functions), the rest of the input (string literals, comments or if nothing is matched, a single character: the .) is being discarded from the lexer immediately (the skip() method).

对于这样的输入:

some valid source
{ 
  function NotAFunction ...
}

procedure Proc
Begin
  ...
End;

procedure Func
Begin
  s = 'function NotAFunction!!!'
End;

将创建以下分析树:

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