"Apfelmus, Heinrich"
Ertugrul Soeylemez wrote:
Let me tell you that usually 90% of my code is monadic and there is really nothing wrong with that. I use especially State monads and StateT transformers very often, because they are convenient and are just a clean combinator frontend to what you would do manually without them: passing state.
The insistence on avoiding monads by experienced Haskellers, in particular on avoiding the IO monad, is motivated by the quest for elegance.
The IO and other monads make it easy to fall back to imperative programming patterns to "get the job done". [...]
Often, the monadic solution _is_ the elegant solution. Please don't confuse monads with impure operations. I use the monadic properties of lists, often together with monad transformers, to find elegant solutions. As long as you're not abusing monads to program imperatively, I think, they are an excellent and elegant structure. I said that 90% of my code is monadic, not that 90% of it is in IO. I do use state monads where there is no more elegant solution than passing state around. It's simply that: you have a structure, which you modify continuously in a complex fashion, such as a neural network or an automaton. Monads are the way to go here, unless you want to do research and find a better way to express this. Personally I prefer this: somethingWithRandomsM :: (Monad m, Random a) => m a -> Something a over these: somethingWithRandoms1 :: [a] -> Something a somethingWithRandoms2 :: RandomGen g => g -> Something a Also I use monads a lot for displaying progress: lengthyComputation :: Monad m => (Progress -> m ()) -> m Result
Consciously excluding monads and restricting the design space to pure functions is the basic tool of thought for finding such elegant abstractions. [...]
You don't need to exclude monads to restrict the design space to pure functions. Everything except IO and ST (and some related monads) is pure. As said, often monads _are_ the elegant solutions. Just look at parser monads. Greets, Ertugrul. -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://blog.ertes.de/