一段Parsec CSV文件的haskell代码

from 《Real World Haskell》-- file: ch16/csv1.hsimport Text.ParserCombinators.Parsec{- A CSV file contains 0 or more lines, each of which is terminated   by the end-of-line character (eol). -}csvFile :: GenParser Char st [[String]]csvFile =     do result <- many line       eof       return result-- Each line contains 1 or more cells, separated by a commaline :: GenParser Char st [String]line =     do result <- cells       eol                       -- end of line       return result       -- Build up a list of cells.  Try to parse the first cell, then figure out -- what ends the cell.cells :: GenParser Char st [String]cells =     do first <- cellContent       next <- remainingCells       return (first : next)-- The cell either ends with a comma, indicating that 1 or more cells follow,-- or it doesn't, indicating that we're at the end of the cells for this lineremainingCells :: GenParser Char st [String]remainingCells =    (char ',' >> cells)            -- Found comma?  More cells coming    <|> (return [])                -- No comma?  Return [], no more cells-- Each cell contains 0 or more characters, which must not be a comma or-- EOLcellContent :: GenParser Char st StringcellContent =     many (noneOf ",\n")       -- The end of line character is \neol :: GenParser Char st Chareol = char '\n'parseCSV :: String -> Either ParseError [[String]]parseCSV input = parse csvFile "(unknown)" input--这个函数经常用，也写在这里了run :: Show a => Parser a -> String -> IO ()run p input        = case (parse p "" input) of            Left err -> do{ putStr "parse error at "                          ; print err                          }            Right x  -> print x