Number guesser iterations

guesser.hs

module Main where

import Data.Char
import Data.List

data Guess 
    = Guess Int Guess Guess
    | GiveUp
    | Done

main = do
    getLine
    guess (guesses 1 100)

guess :: Guess -> IO ()
guess (Guess n lower higher) = do
    print n
    response <- getLine
    guess $ nextGuess response lower higher
guess _ = return ()

nextGuess :: String -> Guess -> Guess -> Guess
nextGuess response lower higher
    | "high" `isInfixOf` r = lower
    | "low"  `isInfixOf` r = higher
    | otherwise            = Done
    where
      r = map toLower response 

guesses :: Int -> Int -> Guess
guesses lo hi | lo > hi   = GiveUp
              | otherwise = Guess mid (guesses lo (mid - 1)) (guesses (mid + 1) hi)
    where
      mid = (lo + hi) `div` 2