gistfile1.txt

*Main> :l markov.hs 
[1 of 1] Compiling Main             ( markov.hs, interpreted )
Ok, modules loaded: Main.
*Main> let x = markovChain 1 5

<interactive>:1:8:
    No instances for (Num (IO b), Ord (IO b))
      arising from a use of `markovChain' at <interactive>:1:8-22
    Possible fix:
      add an instance declaration for (Num (IO b), Ord (IO b))
    In the expression: markovChain 1 5
    In the definition of `x': x = markovChain 1 5
*Main> 

markov.hs

import System.Random

--randomNegate :: (Integral a) => a -> IO a
--markovMain :: (Integral a) => a a -> [a a]
--markovChain :: (Integral a) => a a -> [a a]

randomNegate magnitude = do
    rand <- randomIO :: IO Bool
    if rand
       then return $ negate magnitude
       else return magnitude

markovMain initial range n = do
    up_or_down <- randomNegate 1
    let n1 = n + up_or_down
    if (n1 > (initial + range)) || (n1 < (initial - range))
       then return [n1, up_or_down]
       else markovMain initial range n1

-- markovMain expects `initial range n`, but n starts at initial
markovChain initial range = markovMain initial range initial

--main = do
--    print markovChain 1 5

{--
while true
  up_or_down = randomNegate()
  if !n
    n = initial
  else
    n += up_or_down
  end
  if (n > (initial + range)) || (n < (initial - range))
    [n, up_or_down]
  end
end
--}