Stuart Hungerford
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:
[...]
I'd like to choose and run one of these functions randomly at run time. [...]
Again the lookup approach seems most reasonable. The cleanest way is to define a simple name type for your functions: data FuncIx = FuncA | FuncB deriving (Ord) instance Random FuncIx where ... funcA :: A -> B funcB :: A -> B funcs :: Map FuncIx (A -> B) funcs = M.fromList (zip [FuncA, FuncB] [funcA, funcB]) If you want to go for maximum speed instead: import qualified Data.Vector as V type FuncIx = Int ... funcs :: V.Vector (A -> B) funcs = V.fromList [funcA, funcB] randFunc :: (RandomGen g) => g -> (A -> B, g) randFunc = first (funcs V.!) . randomR (0, 1) Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/