{- 

Running Interactive Programs with Haskell
CSE 341

You should have a module with an action called "main" with type IO ().

Type this on the command line to run the program: 

runhaskell Magic.hs

For some reason, this uses a slightly different I/O library than the
interpreter (at least on Linux and Mac).  As a result, the program has
a nicer input behavior for readLn that understands backspace, ^u, etc.

Although you won't need to do this for CSE341, you can also produce an
executable file.  To produce an executable, the module needs to be
called Main -- the file can be called something other than Main.hs
however.


ghc --make Magic.hs -o magicprogram

'magicprogram' will now be an executable file.

This executable will still have the nicer input behavior that understands
backspace and so on.  But on the output side, Haskell won't flush the
output buffer until it has a complete line of text.  To get around this,
import System.IO, and add this line after the putStr:
  hFlush stdout

-}

module Main
    where

get_magic_number = do
  putStr "Please enter a magic number: " 
  n <- readLn
  if mod n 2 == 0 
    then do putStrLn "Sorry, even numbers are not magic ..."
            get_magic_number
    else return n

main = do
  n <- get_magic_number
  putStrLn ("The magic number is ... " ++ show n ++ "\n\n")