[Haskell-beginners] Buggy behavior of "withFile"

9 Dec 2014

      I've encountered unexplainable of "withFile" function. Consider
"example.hs" program:

    import System.IO

    main = do
        cnts <- withFile "example.hs" ReadMode $ (\h -> do
            res <- hGetContents h
            --putStr res
            return res)
        putStr cnts

When commented-out line is like that, program doesn't write out
anything to the STDOUT.
If "--" (commend characters) are removed, program writes out contents
of "example.hs" two times.

Is this expected behavior? I asked on #haskell (freenode) and one
fellow there found it equally confusing...

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GHC version: The Glorious Glasgow Haskell Compilation System, version 7.6.3
OS: Linux

Thanks,
Zoran Plesivčak