I think the MonadRandom package has a elegant solution for your problem: fromList :: MonadRandomhttp://hackage.haskell.org/packages/archive/MonadRandom/0.1.6/doc/html/Contr...m => [(a, Rationalhttp://hackage.haskell.org/packages/archive/base/4.4.1.0/doc/html/Prelude.ht...)] -> m a Example: fromList [(add, 1), (scale, 1), (rareFunction, 0.1)] On Sun, May 20, 2012 at 8:42 AM, Stuart Hungerford < stuart.hungerford@gmail.com> wrote:
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
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