[Haskell-cafe] Restricted file reading monad

[Jason Dusek]

  This is something of the blind leading the blind, but you seem
  to need a bit of state monad mixed with IO monad. So you could
  look into StateT, a monad transformer, which should make you a
  StateIO monad specialized to FileReader. Then you define a
  `runFileReader` that allows you to jump into the FileReader
  monad.

  I defined a "pointer walking" monad a while back, but that did
  all the IO with `unsafePerformIO`, so I could use a pure State
  monad.

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_jsn