module File(
    countLines
    ) where




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--  To read the full text, see license.txt in the main directory of this repository
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import qualified System.IO as IO




countLines :: FilePath -> IO Int
countLines f = do
    h <- IO.openFile f IO.ReadMode
    e <- IO.hIsEOF h
    if e
        then IO.hClose h >> return 0
        else countLinesTail h 0




countLinesTail :: IO.Handle -> Int -> IO Int
countLinesTail h n = do
    t <- IO.hGetLine h
    e <- IO.hIsEOF h
    if e
        then IO.hClose h >> return (n + 1)
        else countLinesTail h (n + 1)