On Sat, 2011-12-03 at 01:35 +0100, Bas van Dijk wrote:

Here are some benchmark results that compare the original monad-peel, the previous monad-control-0.2.0.3 and the new monad-control-0.3:

http://basvandijk.github.com/monad-control.html

Note that the benchmarks use Bryan O'Sullivan's excellent new criterion-0.6 package.

btw, how did you manage to get measurements from 2 different versions of the same library (monad-control 0.3 and 0.2.0.3) into a single report?

On 12/2/11 7:35 PM, Bas van Dijk wrote:

On 3 December 2011 00:45, Bas van Dijk wrote:

...

* 60 times faster than the previous release!

Here are some benchmark results that compare the original monad-peel, the previous monad-control-0.2.0.3 and the new monad-control-0.3:

http://basvandijk.github.com/monad-control.html

Note that the benchmarks use Bryan O'Sullivan's excellent new criterion-0.6 package.

Those are some beautiful benchmarks. Not only is it much faster, but the distribution is much more peaked, which is always a good thing since it makes the performance more predictable. Kudos. -- Live well, ~wren

On Tue, Dec 6, 2011 at 5:03 AM, Joey Hess wrote:

I'm trying to convert from 0.2 to 0.3, but in way over my head.

{-# LANGUAGE GeneralizedNewtypeDeriving #-} newtype Annex a = Annex { runAnnex :: StateT AnnexState IO a }        deriving (                Monad,                MonadIO,                -- MonadControlIO                MonadBaseControl IO        )

I added that after seeing this when I changed some code to use the new liftBaseOp instead of liftIOOp. (They're equivilant, right?)

   No instance for (MonadBaseControl IO Annex)         arising from a use of `liftBaseOp'

But with ghc 7.0.4, the derivation fails:

Annex.hs:45:17:    Can't make a derived instance of `MonadBaseControl IO Annex'      (even with cunning newtype deriving):      the class has associated types    In the newtype declaration for `Annex'

The only way I can find to make my code compile is to lose the newtype. But of course that makes for some ugly type messages.

-- see shy jo

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Hi Joey, I just spent a fair amount of time yesterday upgrading packages to monad-control 0.3. What I had to do was add in the MonadTransControl and MonadBaseControl instances manually. It's actually not too difficult; just copy out the instance for StateT and make a few changes. Be warned that Bas used some tricky CPP stuff, however, which you'll have to unwind ;). Michael

On Tue, Dec 6, 2011 at 6:04 AM, Joey Hess wrote:

Michael Snoyman wrote:

...

I just spent a fair amount of time yesterday upgrading packages to monad-control 0.3. What I had to do was add in the MonadTransControl and MonadBaseControl instances manually. It's actually not too difficult; just copy out the instance for StateT and make a few changes. Be warned that Bas used some tricky CPP stuff, however, which you'll have to unwind ;).

I forgot to mention that I tried doing that, based on the example in the haddock, but failed miserably. Care to share a working example, perhaps in the form of a patch to the monad-control haddock? :)

-- see shy jo

Maybe this will help[1]. It's using RWST instead of StateT, but it's the same idea. [1] https://github.com/yesodweb/yesod/commit/7619e4e9dd88c152d1e00b6fea073c3d52d...

On Tue, Dec 6, 2011 at 11:49 AM, Bas van Dijk wrote:

On 6 December 2011 05:06, Michael Snoyman wrote:

...

Maybe this will help[1]. It's using RWST instead of StateT, but it's the same idea.

[1] https://github.com/yesodweb/yesod/commit/7619e4e9dd88c152d1e00b6fea073c3d52d...

Hi Michael,

Note that you can just reuse the MonadTransControl instance of the RWST transformer:

instance MonadTransControl (GGWidget master) where    newtype StT (GGWidget master) a =        StWidget {unStWidget :: StT (GWInner master) a}    liftWith f = GWidget $ liftWith $ \run ->                   f $ liftM StWidget . run . unGWidget    restoreT = GWidget . restoreT . liftM unStWidget

Cheers,

Bas

Thanks Bas, I was just in the process of converting Widget from being a RWS to a Writer, and your code made it much simpler :). Michael

On Tue, Dec 6, 2011 at 3:03 PM, Bas van Dijk wrote:

On 6 December 2011 12:59, Michael Snoyman wrote:

...

On Tue, Dec 6, 2011 at 11:49 AM, Bas van Dijk wrote:

...

On 6 December 2011 05:06, Michael Snoyman wrote:

...

Maybe this will help[1]. It's using RWST instead of StateT, but it's the same idea.

[1] https://github.com/yesodweb/yesod/commit/7619e4e9dd88c152d1e00b6fea073c3d52d...

Hi Michael,

Note that you can just reuse the MonadTransControl instance of the RWST transformer:

instance MonadTransControl (GGWidget master) where    newtype StT (GGWidget master) a =        StWidget {unStWidget :: StT (GWInner master) a}    liftWith f = GWidget $ liftWith $ \run ->                   f $ liftM StWidget . run . unGWidget    restoreT = GWidget . restoreT . liftM unStWidget

Cheers,

Bas

Thanks Bas, I was just in the process of converting Widget from being a RWS to a Writer, and your code made it much simpler :).

Michael

Do you think it's useful to have the following two utility functions for defining a MonadTransControl instance for your own monad transformer provided that your transformers is defined in terms of another transformer:

defaultLiftWith ∷ (Monad m, MonadTransControl tInner)                ⇒ (tInner m α → t m α)          -- ^ Constructor                → (∀ β n. t n β → tInner n β)   -- ^ Deconstructor                → (∀ β. StT tInner β → StT t β) -- ^ State constructor                → ((Run t → m α) → t m α) defaultLiftWith con deCon st = \f → con $ liftWith $ \run →                                      f $ liftM st ∘ run ∘ deCon

defaultRestoreT ∷ (Monad m, MonadTransControl tInner)                ⇒ (tInner m α → t m α)      -- ^ Constructor                → (StT t α  → StT tInner α) -- ^ State deconstructor                → (m (StT t α) → t m α) defaultRestoreT con unSt = con ∘ restoreT ∘ liftM unSt

For example in your case you would use these as follows:

instance MonadTransControl (GGWidget master) where    newtype StT (GGWidget master) a =        StWidget {unStWidget :: StT (GWInner master) a}    liftWith = defaultLiftWith GWidget unGWidget StWidget    restoreT = defaultRestoreT GWidget unStWidget

Bas

I don't have a strong opinion, but it sounds like a net win, assuming the documentation clearly explains how they are supposed to be used. Michael

On 6 December 2011 09:12, Bas van Dijk wrote:

instance MonadBaseControl IO Annex where    newtype StM Annex a = StAnnex (StM (StateT AnnexState IO) a)    liftBaseWith f = Annex $ liftBaseWith $ \runInIO ->                       f $ liftM StAnnex . runInIO . runAnnex

Oops forgot the restoreM method: restoreM = Annex . restoreM . unStAnnex unStAnnex (StAnnex st) = st

Bas van Dijk wrote:

You can use the following:

{-# LANGUAGE GeneralizedNewtypeDeriving, TypeFamilies, MultiParamTypeClasses #-}

import Control.Applicative import Control.Monad import Control.Monad.Base import Control.Monad.Trans.Class import Control.Monad.Trans.Control import Control.Monad.Trans.State import Control.Monad.IO.Class

newtype Annex a = Annex { runAnnex :: StateT AnnexState IO a } deriving (Applicative, Functor, Monad, MonadIO)

data AnnexState = AnnexState

instance MonadBase IO Annex where liftBase = Annex . liftBase

instance MonadBaseControl IO Annex where newtype StM Annex a = StAnnex (StM (StateT AnnexState IO) a) liftBaseWith f = Annex $ liftBaseWith $ \runInIO -> f $ liftM StAnnex . runInIO . runAnnex

When I have some time I will add some better documentation to monad-control.

Hmm, very close. With -Wall, I get: Annex.hs:54:10: Warning: No explicit method nor default method for `restoreM' In the instance declaration for `MonadBaseControl IO Annex' And my program crashes at runtime (!) No instance nor default method for class operation Control.Monad.Trans.Control.restoreM -- see shy jo