我试图在 Haskell 中正确读取文件,但似乎收到此错误。
*** 异常:neo.txt:openFile:资源繁忙(文件被锁定)
这是我的代码。
import Data.Char
import Prelude
import Data.List
import Text.Printf
import Data.Tuple
import Data.Ord
import Control.Monad
import Control.Applicative((<*))
import Text.Parsec
( Parsec, ParseError, parse -- Types and parser
, between, noneOf, sepBy, many1 -- Combinators
, char, spaces, digit, newline -- Simple parsers
)
这些是电影领域。
type Title = String
type Director = String
type Year = Int
type UserRatings = (String,Int)
type Film = (Title, Director, Year , [UserRatings])
type Period = (Year, Year)
type Database = [Film]
这是对所有类型的解析,以便从文件中正确读取
-- Parse a string to a string
stringLit :: Parsec String u String
stringLit = between (char '"') (char '"') $ many1 $ noneOf "\"\n"
-- Parse a string to a list of strings
listOfStrings :: Parsec String u [String]
listOfStrings = stringLit `sepBy` (char ',' >> spaces)
-- Parse a string to an int
intLit :: Parsec String u Int
intLit = fmap read $ many1 digit
-- Or `read <$> many1 digit` with Control.Applicative
stringIntTuple :: Parsec String u (String , Int)
stringIntTuple = liftM2 (,) stringLit intLit
film :: Parsec String u Film
film = do
-- alternatively `title <- stringLit <* newline` with Control.Applicative
title <- stringLit
newline
director <- stringLit
newline
year <- intLit
newline
userRatings <- stringIntTuple
newline
return (title, director, year, [userRatings])
films :: Parsec String u [Film]
films = film `sepBy` newline
这是主程序(在winghci中写入“main”来启动程序)
-- The Main
main :: IO ()
main = do
putStr "Enter your Username: "
name <- getLine
filmsDatabase <- loadFile "neo.txt"
appendFile "neo.txt" (show filmsDatabase)
putStrLn "Your changes to the database have been successfully saved."
这是loadFile函数
loadFile :: FilePath -> IO (Either ParseError [Film])
loadFile filename = do
database <- readFile filename
return $ parse films "Films" database
另一个txt文件名为neo,包含一些像这样的电影
"Blade Runner"
"Ridley Scott"
1982
("Amy",5), ("Bill",8), ("Ian",7), ("Kevin",9), ("Emma",4), ("Sam",7), ("Megan",4)
"The Fly"
"David Cronenberg"
1986
("Megan",4), ("Fred",7), ("Chris",5), ("Ian",0), ("Amy",6)
只需复制粘贴同一目录中的所有内容(包括 txt 文件)并测试它以查看我描述的错误。