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tip An example of making the parser more robust with alternation.

Changeset bf5f58b35044…

Parent c381bb2b7e39…

by Profile picture of User 138Hao Lian <hao@fogcreek.com>

Changes to 2 files · Browse files at bf5f58b35044 Showing diff from parent c381bb2b7e39 Diff from another changeset...

Change 1 of 1 Show Changes Only babybearparser/​Parser.fs Stacked
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 module babybearparser.Parser    open FParsec.CharParsers  open FParsec.Primitives  open System    type Keyword = Word of string | Phrase of string    type Filter =   | Author of string   | Date of DateTime * DateTime   | File of string   | Project of string   | Repo of string    type Atom = KeywordAtom of Keyword | FilterAtom of Filter    type ParseError (msg: string) =   inherit Exception (msg)    (* Utilities *)  let pipeline (f, a) = f a  let failIfNone msg = function   | Some x -> preturn x   | None -> fail msg  let stringToDate = function   | "today" -> DateTime.UtcNow.Date |> Some   | "yesterday" -> DateTime.UtcNow.Date.AddDays -1. |> Some   | s -> try DateTime.Parse s |> Some with :? FormatException -> None  let findFilter = function   | "author" -> Author   | "file" -> File   | "project" -> Project   | "repo" -> Repo   | _ -> raise <| ParseError "Invalid filter name"    (* Parsers *)  let word = many1Satisfy <| fun c -> c <> ' '  let phraseEscape = pchar '\\' >>. pchar '"'  let phraseInnard = phraseEscape <|> noneOf "\""  let phraseInnards = manyChars phraseInnard  let phrase = between (pchar '"') (pchar '"') phraseInnards  let keyword = (phrase |>> Phrase) <|> (word |>> Word)    let filterName = ["author"; "file"; "project"; "repo"] |> Seq.map pstring |> choice  let regularFilter =   (filterName |>> findFilter) - .>> (pchar ':') + .>>? (pchar ':')   .>>. (phrase <|> word <?> "filter argument")   |>> pipeline  let dateWord = many1Chars <| noneOf ". "  let fullDate = (phrase <|> dateWord) |>> stringToDate >>= failIfNone "Unrecognized date"  let dateStart = fullDate <|>% DateTime.MinValue  let dateEnd = fullDate <|>% DateTime.UtcNow.Date  let dateFilter = pstring "date:" >>. dateStart .>> pstring ".." .>>. dateEnd |>> Date  let filter = regularFilter <|> dateFilter    let atom = (filter |>> FilterAtom) <|> (keyword |>> KeywordAtom)  let spaces = many1Satisfy <| fun c -> c = ' '  let atoms = sepBy atom spaces  let parse input =   match run atoms input with   | Success (x, _, _) -> x   | Failure (x, _, _) -> raise <| ParseError x
Change 1 of 1 Show Entire File babybearparser/​Testing.fs Stacked
 
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@@ -90,3 +90,16 @@
  member this.TestsInvalidDate() =   let f () = parse "date:\"many moons ago\"..today eggs" |> ignore   throwsParseError f "Unrecognized date" + + [<TestMethod>] + member this.TestsFilterAlternation() = + equals (parse "projects") [KeywordAtom <| Word "projects"] + + [<TestMethod>] + member this.TestsFilterAlternation2() = + equals (parse "proj") [KeywordAtom <| Word "proj"] + + [<TestMethod>] + member this.TestsEmptyFilter2() = + let f () = parse "project:" |> ignore + throwsParseError f "filter argument" \ No newline at end of file