| Copyright | (c) Andy Gill 2001, (c) Oregon Graduate Institute of Science and Technology, 2001, (c) 2015 KONISHI Yohsuke |
|---|---|
| License | BSD-style (see the file LICENSE) |
| Maintainer | ocean0yohsuke@gmail.com |
| Stability | experimental |
| Portability | --- |
| Safe Haskell | Safe |
| Language | Haskell2010 |
DeepControl.Monad.Trans
Contents
Description
This module enables you to program in Monad-Transformer style for more deeper level than the usual Control.Monad.Trans module expresses.
You would realize exactly what much deeper level means by reading the example codes, which are attached on the page bottom.
- module Control.Monad.Trans
- class (Monad m, MonadTrans t) => MonadTrans_ m t | m -> t, t -> m where
- transfold2 :: (Monad m1, MonadTrans_ m2 t2) => m1 (m2 a) -> t2 m1 a
- untransfold2 :: (Monad m1, MonadTrans_ m2 t2) => t2 m1 a -> m1 (m2 a)
- transfold3 :: (Monad m1, Monad (t2 m1), MonadTrans_ m2 t2, MonadTrans_ m3 t3) => m1 (m2 (m3 a)) -> t3 (t2 m1) a
- untransfold3 :: (Monad m1, Monad (t2 m1), MonadTrans_ m2 t2, MonadTrans_ m3 t3) => t3 (t2 m1) a -> m1 (m2 (m3 a))
- transfold4 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4) => m1 (m2 (m3 (m4 a))) -> t4 (t3 (t2 m1)) a
- untransfold4 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4) => t4 (t3 (t2 m1)) a -> m1 (m2 (m3 (m4 a)))
- transfold5 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), Monad (t4 (t3 (t2 m1))), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4, MonadTrans_ m5 t5) => m1 (m2 (m3 (m4 (m5 a)))) -> t5 (t4 (t3 (t2 m1))) a
- untransfold5 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), Monad (t4 (t3 (t2 m1))), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4, MonadTrans_ m5 t5) => t5 (t4 (t3 (t2 m1))) a -> m1 (m2 (m3 (m4 (m5 a))))
Documentation
module Control.Monad.Trans
MonadTrans
class (Monad m, MonadTrans t) => MonadTrans_ m t | m -> t, t -> m where Source
Required only for transfold
Instances
| MonadTrans_ [] ListT Source | |
| MonadTrans_ Identity IdentityT Source | |
| MonadTrans_ Maybe MaybeT Source | |
| MonadTrans_ (Except e) (ExceptT e) Source | |
| Monoid w => MonadTrans_ (Writer w) (WriterT w) Source |
Level-2
trans-roll
transfold2 :: (Monad m1, MonadTrans_ m2 t2) => m1 (m2 a) -> t2 m1 a Source
>>>transfold2 $ [Just 1]MaybeT [Just 1]
>>>transfold2 $ Just [1]ListT (Just [1])
untransfold2 :: (Monad m1, MonadTrans_ m2 t2) => t2 m1 a -> m1 (m2 a) Source
>>>untransfold2 $ MaybeT [Just 1][Just 1]
>>>untransfold2 $ ListT (Just [1])Just [1]
Level-3
trans-roll
transfold3 :: (Monad m1, Monad (t2 m1), MonadTrans_ m2 t2, MonadTrans_ m3 t3) => m1 (m2 (m3 a)) -> t3 (t2 m1) a Source
>>>transfold3 $ ExceptT (Identity (Right [Just 1]))MaybeT (ListT (ExceptT (Identity (Right [Just 1]))))
untransfold3 :: (Monad m1, Monad (t2 m1), MonadTrans_ m2 t2, MonadTrans_ m3 t3) => t3 (t2 m1) a -> m1 (m2 (m3 a)) Source
>>>untransfold3 $ MaybeT (ListT (ExceptT (Identity (Right [Just 1]))))ExceptT (Identity (Right [Just 1]))
Level-4
trans-roll
transfold4 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4) => m1 (m2 (m3 (m4 a))) -> t4 (t3 (t2 m1)) a Source
untransfold4 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4) => t4 (t3 (t2 m1)) a -> m1 (m2 (m3 (m4 a))) Source
Level-5
trans-roll
transfold5 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), Monad (t4 (t3 (t2 m1))), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4, MonadTrans_ m5 t5) => m1 (m2 (m3 (m4 (m5 a)))) -> t5 (t4 (t3 (t2 m1))) a Source
untransfold5 :: (Monad m1, Monad (t2 m1), Monad (t3 (t2 m1)), Monad (t4 (t3 (t2 m1))), MonadTrans_ m2 t2, MonadTrans_ m3 t3, MonadTrans_ m4 t4, MonadTrans_ m5 t5) => t5 (t4 (t3 (t2 m1))) a -> m1 (m2 (m3 (m4 (m5 a)))) Source
Level-2 example
Here is a monad transformer example how to implement Ackermann function improved to stop within a certain limit of time, with ReaderT-IdentityT2-IO-Maybe monad, a level-2 monad-transformation.
import DeepControl.Applicative
import DeepControl.Traversable (sink)
import DeepControl.Monad ((>-))
import DeepControl.Monad.Morph ((|*|), (|>|))
import DeepControl.Monad.Trans (transfold2, untransfold2)
import DeepControl.Monad.Trans.Identity (Identity(..), IdentityT(..), IdentityT2(..))
import Control.Monad.Reader
import Control.Monad.Trans.Maybe
import System.Timeout (timeout)
type TimeLimit = Int
ackermannTimeLimit :: TimeLimit -> Int -> Int ->
IO (Maybe Int) -- IO-Maybe Monad
ackermannTimeLimit timelimit x y = timeout timelimit (ackermannIO x y)
where
ackermannIO :: Int -> Int -> IO Int
ackermannIO 0 n = (.*) $ n + 1
ackermannIO m n | m > 0 && n == 0 = ackermannIO (m-1) 1
| m > 0 && n > 0 = ackermannIO m (n-1) >>= ackermannIO (m-1)
ackermann :: Int -> Int ->
ReaderT TimeLimit (IdentityT2 IO Maybe) Int -- ReaderT-IdentityT2-IO-Maybe monad
ackermann x y = do
timelimit <- ask
(|*|) . IdentityT2 $ ackermannTimeLimit timelimit x y -- lift IO-Maybe function to ReaderT-IdentityT2-IO-Maybe function
calc_ackermann :: TimeLimit -> Int -> Int -> IO (Maybe Int)
calc_ackermann timelimit x y = ackermann x y >- \r -> runReaderT r timelimit
>- runIdentityT2
-- λ> sink $ calc_ackermann 1000 |$> [0..4] |* 4
-- [Just 5,Just 6,Just 11,Just 125,Nothing]
ackermann' :: Int -> Int ->
ReaderT TimeLimit (MaybeT IO) Int -- ReaderT-MaybeT-IO monad
ackermann' x y = (transfold2 . runIdentityT2) |>| ackermann x y -- You can make usual ReaderT-MaybeT-IO function from ReaderT-IdentityT2-IO-Maybe function
ackermann'' :: Int -> Int ->
ReaderT TimeLimit (IdentityT2 IO Maybe) Int -- ReaderT-IdentityT2-IO-Maybe monad
ackermann'' x y = (IdentityT2 . untransfold2) |>| ackermann' x y -- You can make ReaderT-IdentityT2-IO-Maybe function from usual ReaderT-MaybeT-IO function