Bulat Ziganshin wrote:
Hello Gracjan,
Tuesday, June 07, 2005, 2:25:50 PM, you wrote:
class Monad m =>> Ref m r | m -> r where
GP> newRef :: a -> m (r a)
GP> readRef :: r a -> m a
GP> writeRef :: r a -> a -> m ()
may be the following will be even more interesting:
I like it very much!
import Control.Monad
import Data.IORef
infixl 0 =:, +=, -=, =::, <<=
ref = newIORef
val = readIORef
a=:b = writeIORef a b
Pretty shame := is already reserver :(. There is something alike
Graphics.Rendering.OpenGL.GL.StateVar. The use $= for assignment.
Generalizing "variables" (in respect to some monad) seems to be often
reinvented idea :)
As I see this could be generalized to all Ref-like constructs
(IO,ST,others?)
a+=b = modifyIORef a (\a-> a+b)
a-=b = modifyIORef a (\a-> a-b)
a=::b = ((a=:).b) =<< val a
Is this convoluted modify? Why doesn't it use modifyIORef? Or am I wrong?
for :: [a] -> (a -> IO b) -> IO ()
for = flip mapM_
I like:
foreach = flip mapM
foreach_ = flip mapM_
newList = ref []
list <<= x = list =:: (++[x])
Is this append?
push list x = list =:: (x:)
pop list = do x:xs<-val list; list=:xs; return x
main = do
sum <- ref 0
lasti <- ref undefined
for [1..5] $ \i -> do
sum += i
lasti =: i
sum =:: (\sum-> 2*sum+1)
print =<< val sum
print =<< val lasti
xs <- newList
for [1..3] (push xs)
xs <<= 10
xs <<= 20
print =<< val xs
Haskell as ultimate imperative language :)
I use this module to simplify working with references in my program.
The first inteface can be used for IORef/STRef/MVar/TVar and second
for lists and Chan
Then we should create classes for those interfaces.
--
Gracjan
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
