free-concurrent (empty) → 0.1.0.0

raw patch · 5 files changed

+152/−0 lines, 5 filesdep +basesetup-changed

Dependencies added: base

Files

LICENSE +20/−0
README.md +1/−0
Setup.hs +2/−0
free-concurrent.cabal +25/−0
src/Control/Concurrent/Free.hs +104/−0

+ LICENSE view

@@ -0,0 +1,20 @@+Copyright (c) 2015 Sam Rijs++Permission is hereby granted, free of charge, to any person obtaining+a copy of this software and associated documentation files (the+"Software"), to deal in the Software without restriction, including+without limitation the rights to use, copy, modify, merge, publish,+distribute, sublicense, and/or sell copies of the Software, and to+permit persons to whom the Software is furnished to do so, subject to+the following conditions:++The above copyright notice and this permission notice shall be included+in all copies or substantial portions of the Software.++THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

+ README.md view

@@ -0,0 +1,1 @@+# haskell-free-concurrent

+ Setup.hs view

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

+ free-concurrent.cabal view

@@ -0,0 +1,25 @@+-- Initial free-concurrent.cabal generated by cabal init.  For further +-- documentation, see http://haskell.org/cabal/users-guide/++name:                free-concurrent+version:             0.1.0.0+synopsis:            Free monads suitable for concurrent computation+-- description:         +homepage:            https://github.com/srijs/haskell-free-concurrent+license:             MIT+license-file:        LICENSE+author:              Sam Rijs+maintainer:          srijs@airpost.net+-- copyright:           +category:            Concurrency+build-type:          Simple+extra-source-files:  README.md+cabal-version:       >=1.10++library+  exposed-modules:     Control.Concurrent.Free+  -- other-modules:       +  -- other-extensions:    +  build-depends:       base >=4.8 && <4.9+  hs-source-dirs:      src+  default-language:    Haskell2010

+ src/Control/Concurrent/Free.hs view

@@ -0,0 +1,104 @@+{-# LANGUAGE GADTs #-}+{-# LANGUAGE RankNTypes #-}++module Control.Concurrent.Free where++import Control.Concurrent+import Control.Concurrent.MVar+import Control.Exception (SomeException(..), try, throwIO)+import Control.Monad (join)++-- | The combination of a free functor, a free applicative functor,+--   and free monad over @f@.+--+--   The semantics of the 'Functor', 'Applicative' and 'Monad' instances+--   are such that it tries to pick the lowest possible abstraction to+--   perform the operation.+--+--   This means that if a computation is constructed using 'fmap', 'pure'+--   and '<*>', it can be parallelised up until the point where the first+--   monadic 'join' sits.+data F f a where+  Pure :: a -> F f a+  Ap   :: f x -> (x -> a) -> F f (a -> b) -> F f b+  Join :: F f (F f a) -> F f a++instance Functor (F f) where+  fmap f (Pure a) = Pure (f a)+  fmap f (Ap x g y) = Ap x g (fmap f <$> y)+  fmap f (Join x) = Join (fmap f <$> x)++instance Applicative (F f) where+  pure = Pure+  Pure f <*> y = fmap f y+  Ap x g y <*> z = Ap x g (flip <$> y <*> z)+  Join x <*> y = Join ((\z -> z <*> y) <$> x)++instance Monad (F f) where+  return = pure+  Pure x >>= f = f x+  x >>= f = Join (fmap f x)+  x >> y = x *> y++-- | Lifts an @f a@ into a @F f a@.+liftF :: f a -> F f a+liftF x = Ap x id (Pure id)++-- | Given a natural transformation from @f@ to @g@ this gives a monoidal natural transformation from @F f@ to @F g@.+hoist :: (forall a. f a -> g a) -> F f a -> F g a+hoist f (Pure a) = Pure a+hoist f (Ap x g y) = Ap (f x) g (hoist f y)+hoist f (Join x) = Join (hoist f (fmap (hoist f) x))++-- | Partially interprets the free monad over @f@ using the semantics for 'pure' and '<*>' given by the 'Applicative' instance for @f@. If it encounters a monadic join, the result is 'Nothing'.+retractA :: Applicative f => F f a -> Maybe (f a)+retractA (Pure a) = Just (pure a)+retractA (Ap x g y) = (\z -> z <*> fmap g x) <$> retractA y+retractA (Join x) = Nothing++-- | Interprets the free monad over @f@ using the semantics for 'return' and '>>=' given by the 'Monad' instance for @f@.+retractM :: Monad f => F f a -> f a+retractM (Pure a) = pure a+retractM (Ap x g y) = retractM y >>= \z -> z <$> g <$> x+retractM (Join x) = join . retractM $ fmap retractM x++-- | Interprets the free monad over @f@ using the+--   transformation from @f@ to @m m@.+--+--   The semantics of the concurrency are given by the transformation,+--   which produces a result that is unwrapped in two stages:+--   The first monadic layer should spawn the concurrent action,+--   and reveal the second layer, which should block+--   until the spawned action has returned with a result.+foldConcurrentM :: Monad m => (forall x. f x -> m (m x)) -> F f a -> m a+foldConcurrentM run (Pure x) = return x+foldConcurrentM run (Ap x g y) = do+  v <- run x+  f <- foldConcurrentM run y+  f . g <$> v+foldConcurrentM run (Join x) = do+  y <- foldConcurrentM run x+  foldConcurrentM run y++-- | Interprets the free monad over 'IO' using concurrent semantics, meaning multiple actions may run in parallel.+retractConcurrentIO :: F IO a -> IO a+retractConcurrentIO = foldConcurrentM $ \action -> do+  v <- newEmptyMVar+  forkIO $ try action >>= putMVar v+  return $ do+    r <- takeMVar v+    case r of+      Left (SomeException e) -> throwIO e+      Right a -> return a++-- | Given a natural transformation from @f@ to @g@, this gives a partial monoidal natural transformation from @F f@ to @g@.+foldA :: Applicative g => (forall x. f x -> g x) -> F f a -> Maybe (g a)+foldA f = retractA . hoist f++-- | Given a natural transformation from @f@ to @m@, this gives a canonical monoidal natural transformation from @F f@ to @m@.+foldM :: Monad m => (forall x. f x -> m x) -> F f a -> m a+foldM f = retractM . hoist f++-- | Given a natural transformation from @f@ to 'IO', this gives a natural transformation from @F f@ to @IO@ where the actions may run concurrently.+foldConcurrentIO :: (forall x. f x -> IO x) -> F f a -> IO a+foldConcurrentIO f = retractConcurrentIO . hoist f