On Thu, 2011-01-06 at 12:35 -0500, Tyson Whitehead wrote:
On January 6, 2011 11:42:09 Iavor Diatchki wrote:
AFAIU, In applicative style programming "join" has proven to be a lot more useful than "bind".
I am not sure what you mean here, I find the "do" notation quite useful.
I think he was meaning when you are using monads in a more "function style" (applicative) than "imperative style" (do notation).
As an example, consider the definition of ">>=" using join and the "$" and "<$>" application operators
x >>= f = join $ f <$> x
versus that using "do" notation
x >>= f = do x' <- x f x'
I guess that in both cases it should be written as x >>= f. Maybe better example: doA :: String -> String -> String -> IO String doB :: IO String doC = join $ doA <$> doB <*> doB <*> doB vs. doC = do x <- doB y <- doB z <- doB doA x y z
Obviously both notations have their places, "do" is usually nicer if I want to use values multiple times, while "applicative style" is usually nicer if I am just unpacking values for an application. I suspect "do", however, tends to get overused simply because that is what monad tutorials teach.
Cheers! -Tyson
I noticed that for people unfamiliar with Haskell the do notation is simpler. However as they get used to they learn to appreciate: data Function = Function Ident Args Type function = Function <$> ident <*> args <*> returnType or similar constructions in simpler ('applicative') cases. Regards