[Haskell-beginners] Choosing a function randomly...

[Stuart Hungerford]

Hi,

This is kind-of related to my earlier question on looking up functions
by name.  Suppose I have a module with a number of functions with the
same signature:

scale :: Int -> Int -> Int

scale s x = s * x

add :: Int -> Int -> Int

add a x = a + x

...

I'd like to choose and run one of these functions randomly at run
time. I can see I could use some kind of case expression:

op :: Int -> Int -> Int

op p x = case random(1,2) of
   1 -> scale p x
   2 -> add p x

Or some kind of pattern guards:

op p x
  | random(1,2) == 1 = scale p x
  | otherwise  = add p x

Although that method won't work as is for more than two choices.  Are
these methods the most idiomatic way of randomly choosing a function?
 How hard would it be to use the machinery of the QuickCheck library
for this, given it must be doing something similar in test suites?

Thanks,

Stu