Due 5PM Friday, October 29.

Chapter 14:

1. Exercise 14.2 in SOE, but, as before, only for the 2nd fold law in Table 11.1,
   and the third take/drop law in Table 11.2.  If the property does not hold for infinite lists, state so, and why.
    
2. Exercise 14.3 in SOE.
    
3. Exercise 14.5 in SOE.

Chapter 16:

4. A mutable variable, or reference, in Haskell might have the following interface:
    
   newRef :: a -> IO (Ref a)
   setRef :: Ref a -> a -> IO ()
   getRef :: Ref a -> IO a
    
   For example, here's a program that creates a reference with an initial value of 42, then adds it to itself, finally printing out the final value:
    
   do r <- newRef 42
      v <- getRef r
      setRef r (v+v)
      v' <- getRef r
      print v'
    
   Define these three functions using first-class channels in Haskell.  You should use good abstraction techniques to make the implementation completely opaque to the user.

Solutions.