当前位置：文江博客话题详情

fparsec 中的位置信息

发布于 2024-11-15 20:04:46 字数 111 浏览 5 评论 0原文

我的 AST 模型需要携带位置信息（文件名、行、索引）。有没有内置的方法来访问这些信息？从参考文档来看，流似乎带有位置，但我更希望不必实现虚拟解析器来保存位置，并将其添加到任何地方。

提前致谢

原文

分享到QQ

分享到微博

如果你对这篇内容有疑问，欢迎到本站社区发帖提问参与讨论，获取更多帮助，或者扫码二维码加入 Web 技术交流群。

发布评论

需要登录才能够评论，你可以免费注册一个本站的账号。

傾城如夢未必闌珊 2024-11-22 20:04:46

解析器实际上是从流到回复的函数的类型缩写：

Parser<_,_> is just CharStream<_> -> Reply<_>

记住这一点，您可以轻松地为位置编写自定义解析器：

let position : CharStream<_> -> Reply<Position> = fun stream -> Reply(stream.Position)
(* OR *)
let position : Parser<_,_> = fun stream -> Reply stream.Position

并将位置信息附加到使用

position .>>. yourParser (*or tuple2 position yourParser*)

位置解析器解析的每个位，不会消耗任何输入，因此可以安全地以这种方式结合起来。

您可以将所需的代码更改限制在一行内，并避免无法控制的代码传播：

type AST = Slash of int64
         | Hash  of int64

let slash : Parser<AST,_> = char '/' >>. pint64 |>> Slash
let hash  : Parser<AST,_> = char '#' >>. pint64 |>> Hash
let ast   : Parser<AST,_> = slash <|> hash

(*if this is the final parser used for parsing lists of your ASTs*)
let manyAst  : Parser<            AST  list,_> = many                (ast  .>> spaces)

let manyAstP : Parser<(Position * AST) list,_> = many ((position .>>. ast) .>> spaces)
(*you can opt in to parse position information for every bit
  you parse just by modifiying only the combined parser     *)

更新：FParsec 有一个预定义的位置解析器：
http://www.quanttec.com/fparsec/reference/charparsers.html #members.getPosition

Parsers are actually type abbreviations for functions from streams to replies:

Parser<_,_> is just CharStream<_> -> Reply<_>

Keeping that in mind, you can easily write a custom parser for positions:

let position : CharStream<_> -> Reply<Position> = fun stream -> Reply(stream.Position)
(* OR *)
let position : Parser<_,_> = fun stream -> Reply stream.Position

and atttach position information to every bit you parse using

position .>>. yourParser (*or tuple2 position yourParser*)

position parser does not consume any input and thus it is safe to combine in that way.

You can keep the code change required restricted to a single line and avoid uncontrollable code spread:

type AST = Slash of int64
         | Hash  of int64

let slash : Parser<AST,_> = char '/' >>. pint64 |>> Slash
let hash  : Parser<AST,_> = char '#' >>. pint64 |>> Hash
let ast   : Parser<AST,_> = slash <|> hash

(*if this is the final parser used for parsing lists of your ASTs*)
let manyAst  : Parser<            AST  list,_> = many                (ast  .>> spaces)

let manyAstP : Parser<(Position * AST) list,_> = many ((position .>>. ast) .>> spaces)
(*you can opt in to parse position information for every bit
  you parse just by modifiying only the combined parser     *)

Update: FParsec has a predefined parser for positions:
http://www.quanttec.com/fparsec/reference/charparsers.html#members.getPosition

回复收藏 0 原文

~没有更多了~