Move Set 11b Ex 5 to Set 13b

exercises/Set11b.hs

@@ -82,34 +82,6 @@ doubleCall op = todo
 compose :: (a -> IO b) -> (c -> IO a) -> c -> IO b
 compose op1 op2 c = todo
 
-------------------------------------------------------------------------------
--- Ex 5: Implement the operation mkCounter that produces the IO operations
--- inc :: IO () and get :: IO Int. These operations should work like this:
---
---   get returns the number of times inc has been called
---
--- In other words, a simple stateful counter. Use an IORef to store the count.
---
--- Note: this is an IO operation that produces two IO operations. Thus
--- the type of mkCounter is IO (IO (), IO Int).
---
--- This exercise is tricky. Feel free to leave it until later.
---
--- An example of how mkCounter works in GHCi:
---
---  *Set11b> (inc,get) <- mkCounter
---  *Set11b> inc
---  *Set11b> inc
---  *Set11b> get
---  2
---  *Set11b> inc
---  *Set11b> inc
---  *Set11b> get
---  4
-
-mkCounter :: IO (IO (), IO Int)
-mkCounter = todo
-
 ------------------------------------------------------------------------------
 -- Ex 6: Reading lines from a file. The module System.IO defines
 -- operations for Handles, which represent open files that can be read