module Control.Proxy.Trans.Writer (
WriterP,
writer,
writerT,
writerP,
runWriterP,
runWriterK,
execWriterP,
execWriterK,
tell,
censor
) where
import Control.Applicative (Applicative(pure, (<*>)), Alternative(empty, (<|>)))
import Control.Monad (MonadPlus(mzero, mplus))
import Control.Monad.IO.Class (MonadIO(liftIO))
import Control.Monad.Morph (MFunctor(hoist))
import Control.Monad.Trans.Class (MonadTrans(lift))
import Control.Proxy.Class (
Proxy(request, respond, (->>), (>>~), (>\\), (//>), turn),
ProxyInternal(return_P, (?>=), lift_P, liftIO_P, hoist_P, thread_P),
MonadPlusP(mzero_P, mplus_P) )
import Control.Proxy.Morph (PFunctor(hoistP))
import Control.Proxy.Trans (ProxyTrans(liftP))
import Data.Monoid (Monoid(mempty, mappend))
newtype WriterP w p a' a b' b (m :: * -> *) r
= WriterP { unWriterP :: w -> p (a', w) (a, w) (b', w) (b, w) m (r, w) }
instance (Monad m, Proxy p) => Functor (WriterP w p a' a b' b m) where
fmap f p = WriterP (\w0 ->
unWriterP p w0 ?>= \(x, w1) ->
return_P (f x, w1) )
instance (Monad m, Proxy p) => Applicative (WriterP w p a' a b' b m) where
pure = return
fp <*> xp = WriterP (\w0 ->
unWriterP fp w0 ?>= \(f, w1) ->
unWriterP xp w1 ?>= \(x, w2) ->
return_P (f x, w2) )
instance (Monad m, Proxy p) => Monad (WriterP w p a' a b' b m) where
return = return_P
(>>=) = (?>=)
instance (Proxy p) => MonadTrans (WriterP w p a' a b' b) where
lift = lift_P
instance (Proxy p) => MFunctor (WriterP w p a' a b' b) where
hoist = hoist_P
instance (MonadIO m, Proxy p) => MonadIO (WriterP w p a' a b' b m) where
liftIO = liftIO_P
instance (Monad m, MonadPlusP p) => Alternative (WriterP w p a' a b' b m) where
empty = mzero
(<|>) = mplus
instance (Monad m, MonadPlusP p) => MonadPlus (WriterP w p a' a b' b m) where
mzero = mzero_P
mplus = mplus_P
instance (Proxy p) => ProxyInternal (WriterP w p) where
return_P = \r -> WriterP (\w -> return_P (r, w))
m ?>= f = WriterP (\w ->
unWriterP m w ?>= \(a, w') ->
unWriterP (f a) w' )
lift_P m = WriterP (\w -> lift_P (m >>= \r -> return (r, w)))
hoist_P nat p = WriterP (\w -> hoist_P nat (unWriterP p w))
liftIO_P m = WriterP (\w -> liftIO_P (m >>= \r -> return (r, w)))
thread_P p w = WriterP (\w' ->
((up ->> thread_P (unWriterP p w') w) >>~ dn) ?>= next )
where
up ((a', w1), w2) =
request ((a', w2 ), w1 ) ?>= \((a , w1'), w2') ->
respond ((a , w2'), w1') ?>= up
dn ((b , w1), w2) =
respond ((b , w2 ), w1 ) ?>= \((b', w1'), w2') ->
request ((b', w2'), w1') ?>= dn
next ((r, w1), w2) = return_P ((r, w2), w1)
instance (Proxy p) => Proxy (WriterP w p) where
fb' ->> p = WriterP (\w ->
(\(b', w') -> unWriterP (fb' b') w') ->> unWriterP p w )
p >>~ fb = WriterP (\w ->
unWriterP p w >>~ (\(b, w') -> unWriterP (fb b) w') )
request = \a' -> WriterP (\w -> request (a', w))
respond = \b -> WriterP (\w -> respond (b , w))
fb' >\\ p = WriterP (\w ->
(\(b', w') -> unWriterP (fb' b') w') >\\ unWriterP p w )
p //> fb = WriterP (\w ->
unWriterP p w //> (\(b, w') -> unWriterP (fb b) w') )
turn p = WriterP (\w -> turn (unWriterP p w))
instance (MonadPlusP p) => MonadPlusP (WriterP w p) where
mzero_P = WriterP (\_ -> mzero_P)
mplus_P m1 m2 = WriterP (\w -> mplus_P (unWriterP m1 w) (unWriterP m2 w))
instance ProxyTrans (WriterP w) where
liftP m = WriterP (thread_P m)
instance PFunctor (WriterP w) where
hoistP nat p = WriterP (\s -> nat (unWriterP p s))
writer :: (Monad m, Proxy p, Monoid w) => (r, w) -> WriterP w p a' a b' b m r
writer x = writerP (return_P x)
writerT :: (Monad m, Proxy p, Monoid w) => m (r, w) -> WriterP w p a' a b' b m r
writerT m = writerP (lift_P m)
writerP
:: (Monad m, Proxy p, Monoid w)
=> p a' a b' b m (r, w) -> WriterP w p a' a b' b m r
writerP p = WriterP (\w ->
thread_P p w ?>= \((r, w2), w1) ->
let w' = mappend w1 w2
in w' `seq` return_P (r, w') )
runWriterP
:: (Monad m, Proxy p, Monoid w)
=> WriterP w p a' a b' b m r -> p a' a b' b m (r, w)
runWriterP p = up >\\ unWriterP p mempty //> dn
where
up (a', w) =
request a' ?>= \a ->
return_P (a , w)
dn (b , w) =
respond b ?>= \b' ->
return_P (b', w)
runWriterK
:: (Monad m, Proxy p, Monoid w)
=> (q -> WriterP w p a' a b' b m r) -> (q -> p a' a b' b m (r, w))
runWriterK k q = runWriterP (k q)
execWriterP
:: (Monad m, Proxy p, Monoid w)
=> WriterP w p a' a b' b m r -> p a' a b' b m w
execWriterP m = runWriterP m ?>= \(_, w) -> return_P w
execWriterK
:: (Monad m, Proxy p, Monoid w)
=> (q -> WriterP w p a' a b' b m r) -> (q -> p a' a b' b m w)
execWriterK k q = execWriterP (k q)
tell :: (Monad m, Proxy p, Monoid w) => w -> WriterP w p a' a b' b m ()
tell w' = WriterP (\w ->
let w'' = mappend w w' in w'' `seq` return_P ((), w''))
censor
:: (Monad m, Proxy p, Monoid w)
=> (w -> w) -> WriterP w p a' a b' b m r -> WriterP w p a' a b' b m r
censor f p = WriterP (\w0 ->
unWriterP p w0 ?>= \(r, w1) ->
return_P (r, f w1) )