module Main where
import System.Random

{-
This exercise asks you to use the I/O Monad to implement a simple
number guessing game by filling in the definitions of a couple of
functions in this file.  In this game, the program selects a random
integer in the set {1 . . . 10} that the player has to guess. The
player guesses by entering a number at the prompt. If the player does
not guess correctly, the program tells the player if the guess was too
high or low, and asks for another guess. Otherwise, the program prints
a congratulatory message and exits.  

Here is an example session:

>./IO2
I'm thinking of a number between 1 and 10.  Can you guess it?
5
Too low!
8
Too low!
9
Too low!
10
Congratulations!


(a) The game asks the player to guess until the player guesses
correctly. To implement this behavior, it is useful to have a control
structure that executes an action until some condition is true (in our
case, the player guessing correctly.)  Fill in the code for untilIO 
below. The function untilIO takes an IO action producing a Bool
and returns an IO action producing nothing: 

  untilIO :: IO Bool -> IO ().

The function untilIO should first execute the loop body (the
argument) and then check the loop condition (the Bool produced by the
argument). If the loop condition returns True, untilIO should exit.
-}


untilIO :: IO Bool -> IO ()
untilIO action = do
-- FILL IN CODE HERE



{-
(b) Now implement the core of the game, 
    doGuess :: Int -> IO Bool, 
which takes the randomly-generated secret number as an argument, gets
the player’s current guess using an IO action, prints whether the
guess was low (Too low!), high (Too high!), or just right
(Congratulations!), and returns a Bool indicating whether the player
finished the game.  -}

-- Some useful functions:
--   getLine :: IO String              -- Reads a line of input
--   read :: String -> Int             -- converts a string of digits into an Int
--   (Or more generally:
--   read :: Read t => String -> t     -- Parse any type t belonging to Read class to a value of type t)
--   putStrLn :: String -> IO ()       -- Print string to output


doGuess :: Int -> IO Bool
doGuess secret = do
-- FILL IN CODE HERE


-- To make an executable called "IO2"
-- >ghc --make IO2.hs

-- To run in the interpretor:
-- >ghci IO2.hs
-- *Main>main

main :: IO ()
main = do
 {  secret <- randomRIO(1,10)
 ;  putStrLn "I'm thinking of a number between 1 and 10.  Can you guess it?"
 ;  untilIO (doGuess secret)
 ;  putStrLn "Congratulations!"
 }