如何使用 FParsec 解析注释

发布于 2024-12-20 05:48:03 字数 1109 浏览 4 评论 0原文

我正在尝试使用 FParsec 从 s 表达式语言解析 lisp 风格的注释。我在上一个线程中解析单行注释方面得到了一些帮助 - 如何转换一个 FParsec 解析器来解析空格

虽然这个问题已经解决，但我仍然需要解析多行注释。这是当前的代码 -

/// Read whitespace character as a string.
let spaceAsStr = anyOf whitespaceChars |>> fun chr -> string chr

/// Read a line comment.
let lineComment = pchar lineCommentChar >>. restOfLine true

/// Read a multiline comment.
/// TODO: make multiline comments nest.
let multilineComment =
    between
        (pstring openMultilineCommentStr)
        (pstring closeMultilineCommentStr)
        (charsTillString closeMultilineCommentStr true System.Int32.MaxValue)

/// Read whitespace text.
let whitespace =
    lineComment <|>
    multilineComment <|>
    spaceAsStr

/// Skip any white space characters.
let skipWhitespace = skipMany whitespace

/// Skip at least one white space character.
let skipWhitespace1 = skipMany1 whitespace

不幸的是，multilineComment 解析永远不会成功。由于这是一个组合器，我无法设置断点或分析它为什么不起作用。

有什么想法为什么它不起作用吗？

原文

I'm attempting to parse lisp-style comments from an s-expression language with FParsec. I got a bit of help with parsing single-line comments in this previous thread - How to convert an FParsec parser to parse whitespace

While that was resolved, I still need to parse multiline comments. Here's the current code -

/// Read whitespace character as a string.
let spaceAsStr = anyOf whitespaceChars |>> fun chr -> string chr

/// Read a line comment.
let lineComment = pchar lineCommentChar >>. restOfLine true

/// Read a multiline comment.
/// TODO: make multiline comments nest.
let multilineComment =
    between
        (pstring openMultilineCommentStr)
        (pstring closeMultilineCommentStr)
        (charsTillString closeMultilineCommentStr true System.Int32.MaxValue)

/// Read whitespace text.
let whitespace =
    lineComment <|>
    multilineComment <|>
    spaceAsStr

/// Skip any white space characters.
let skipWhitespace = skipMany whitespace

/// Skip at least one white space character.
let skipWhitespace1 = skipMany1 whitespace

Unfortunately, the multilineComment parse never succeeds. Since this is a combinator, I can't put breakpoints or analyze why it won't work.

Any ideas why it won't work?

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情深缘浅 2024-12-27 05:48:03

尝试将 closeMultilineCommentStr 的 bool 参数更改为 false，

(charsTillString closeMultilineCommentStr false System.Int32.MaxValue)

否则它将跳过 closeMultilineCommentStr 字符串。

使其与嵌套注释一起使用

let rec multilineComment o=
    let ign x = charsTillString x false System.Int32.MaxValue
    between
        (pstring openMultilineCommentStr)
        (pstring closeMultilineCommentStr)
        (attempt (ign openMultilineCommentStr >>. multilineComment >>. ign closeMultilineCommentStr) <|> 
        ign closeMultilineCommentStr) <|o

Try changing the bool argument for closeMultilineCommentStr to false

(charsTillString closeMultilineCommentStr false System.Int32.MaxValue)

Otherwise it will skip over the closeMultilineCommentStr string.

To make it work with nested comments

let rec multilineComment o=
    let ign x = charsTillString x false System.Int32.MaxValue
    between
        (pstring openMultilineCommentStr)
        (pstring closeMultilineCommentStr)
        (attempt (ign openMultilineCommentStr >>. multilineComment >>. ign closeMultilineCommentStr) <|> 
        ign closeMultilineCommentStr) <|o

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