FParsec和基于分隔符的语法

问题描述

我正在尝试使用fparsec解析简单的待办事项列表语言(实际上是TaskPaper的数据)作为简单的解析器组合器示例.但是我遇到了一个我似乎无法迷惑的错误.我是解析器组合器的新手，FParsec似乎依赖于我了解Parsec，但是我发现parsec文档难以理解.

I'm trying to use fparsec to parse a simple todo list language (the data from TaskPaper actually) as a simple parser combinator example. But I've run into a bug I can't seem to puzzle out. I'm new to parser combinators and FParsec seems to rely on me knowing Parsec, but I'm finding the parsec documentation inscrutable.

任务文件语言的规则很简单(我暂时忽略了@tags)

The rules of the task paper language are simple (I'm ignoring @tags for now)

• 项目以':'
结尾
• 任务以-"开头
• 任何其他文本行都是有关项目或任务的纯文本注释

因此，字符串"Project 1:\ nSome note \ nProject 2:"应从parseFile返回为[ProjectName("Project 1"); NoteText("Some note"); ProjectName("Project 2")]]，但是相反，我得到了[ProjectName("Project 1"); ProjectName("Some note \ nProject 2")]

So the string "Project 1:\nSome note\nProject 2:" should return from parseFile as [ProjectName("Project 1");NoteText("Some note");ProjectName("Project 2")], but instead, I get [ProjectName("Project 1");ProjectName("Some note\nProject 2")]

下面是我的解析器代码.

Below is my parser code.

open FParsec.Primitives
open FParsec.CharParsers
type ProjectAst = ProjectName of string
                    | TaskText of string
                    | NoteText of string

let asString (x:char list) :string =
    x
    |> List.map (fun y -> y.ToString())
    |> String.concat ""
let makeNote x = NoteText(asString x)
let parseProject =
    parse { let! s = many (noneOf ":\n\r\c")
            do! skipChar ':'
            return ProjectName( asString s ) }
let parseTask =
    parse { do! skipChar '-'
            let! s = many (noneOf "\n\r\c")
            return TaskText( asString s) }
let parseNote = many (noneOf "\n\r\c") |>> makeNote

let parseLine = parseTask <|> (attempt parseProject) <|> parseNote
let parseFile = sepBy parseLine (many1 whitespace)

已编辑

语法来自Hogbay Software的TaskPaper应用程序 TaskPaper网站语法示例

The syntax is taken from Hogbay Software's TaskPaper application TaskPaper websiteSome examples of the syntax

    Project 1:
    Description of Project One
    -task for project 1
    -another task for project 1
    details for another task
    -final task

    Go to store:
    -buy eggs
    -buy milk

推荐答案

我在FParsec方面不是很流利，但是这种方法很有效:

I'm not super fluent in FParsec, but this one works:

let newline = pchar '\n'
let notNewLine = noneOf "\n"
let allTillEOL = manyChars notNewLine

let parseProject = 
    let r = manyCharsTill (noneOf ":\n") (pchar ':')
    r |>> ProjectName

let parseTask = 
    let r = skipChar '-' >>. allTillEOL
    r |>> TaskText

let parseNote = allTillEOL |>> NoteText

let parseLine = parseTask <|> attempt parseProject <|> parseNote
let parseFile = sepBy parseLine newline

let a = run parseFile "Project 1:\nSome note\nProject 2:\n-One Task"
match a with
| Success (a,b,c) -> printfn "%A" a
| Failure (a,b,c) -> printfn "failed: %s" a

打印出:

[ProjectName "Project 1"; NoteText "Some note"; ProjectName "Project 2"; TaskText "One Task"]

我将对照其他示例对其进行测试.

I'd test it against other examples.

顺便说一句:几次使用FParsec时，我更喜欢组合器风格而不是单子风格.

BTW: the few times I've used FParsec I've preferred the combinator style over monadic style.

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