ocamlyacc分析错误:什么令牌? [英] ocamlyacc parse error: what token?

问题描述

我正在使用ocamlyacc和ocamllex.我的语法中有错误产生，表示发生自定义异常.到目前为止，我可以报告错误位置了:

I'm using ocamlyacc and ocamllex. I have an error production in my grammar that signals a custom exception. So far, I can get it to report the error position:

| error { raise (Parse_failure (string_of_position (symbol_start_pos ()))) }

但是，我也想知道读取了哪个令牌.必须有一种方法-有人知道吗?

But, I also want to know which token was read. There must be a way---anyone know?

谢谢.

推荐答案

令牌是由lexer生成的，因此，当发生错误时，您可以使用当前的lexer令牌:

Tokens are generated by lexer, hence you can use the current lexer token when error occurs :

  let parse_buf_exn lexbuf =
    try
      T.input T.rule lexbuf
    with exn ->
      begin
        let curr = lexbuf.Lexing.lex_curr_p in
        let line = curr.Lexing.pos_lnum in
        let cnum = curr.Lexing.pos_cnum - curr.Lexing.pos_bol in
        let tok = Lexing.lexeme lexbuf in
        let tail = Sql_lexer.ruleTail "" lexbuf in
        raise (Error (exn,(line,cnum,tok,tail)))
      end

Lexing.lexeme lexbuf是您所需要的.其他部分不是必需的，而是有用的. ruleTail将所有剩余标记合并为字符串，以便用户轻松定位错误位置. lexbuf.Lexing.lex_curr_p应该在词法分析器中更新以包含正确的位置. (源)

Lexing.lexeme lexbuf is what you need. Other parts are not necessary but useful. ruleTail will concat all remaining tokens into string for the user to easily locate error position. lexbuf.Lexing.lex_curr_p should be updated in the lexer to contain correct positions. (source)

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