unliftio-core (empty) → 0.1.0.0

raw patch · 6 files changed

+166/−0 lines, 6 filesdep +basedep +transformerssetup-changed

Dependencies added: base, transformers

Files

• ChangeLog.md +3/−0
• LICENSE +20/−0
• README.md +6/−0
• Setup.hs +2/−0
• src/Control/Monad/IO/Unlift.hs +102/−0
• unliftio-core.cabal +33/−0

@@ -0,0 +1,3 @@+## 0.1.0.0++* Initial release

@@ -0,0 +1,20 @@+Copyright (c) 2017 FP Complete++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.

@@ -0,0 +1,6 @@+# unliftio-core++Provides the core `MonadUnliftIO` typeclass, instances for `base` and+`transformers`, and basic utility functions. Typically, you'll want to use the+[unliftio](https://www.stackage.org/package/unliftio) library, which provides+more functionality (and a much better description).

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

@@ -0,0 +1,102 @@+{-# LANGUAGE RankNTypes #-}+-- | Please see the README.md file for information on using this+-- package.+module Control.Monad.IO.Unlift+  ( MonadUnliftIO (..)+  , UnliftIO (..)+  , askRunInIO+  , withUnliftIO+  , withRunInIO+  , toIO+  , MonadIO (..)+  ) where++import Control.Monad (liftM)+import Control.Monad.IO.Class+import Control.Monad.Trans.Reader (ReaderT (..))+import Control.Monad.Trans.Identity (IdentityT (..))++-- | The ability to run any monadic action @m a@ as @IO a@.+--+-- This is more precisely a natural transformation. We need to new+-- datatype (instead of simply using a @forall@) due to lack of+-- support in GHC for impredicative types.+--+-- @since 0.1.0.0+newtype UnliftIO m = UnliftIO { unliftIO :: forall a. m a -> IO a }++-- | Monads which allow their actions to be run in 'IO'.+--+-- While 'MonadIO' allows an 'IO' action to be lifted into another+-- monad, this class captures the opposite concept: allowing you to+-- capture the monadic context. Note that, in order to meet the laws+-- given below, the intuition is that a monad must have no monadic+-- state, but may have monadic context. This essentially limits+-- 'MonadUnliftIO' to 'ReaderT' and 'IdentityT' transformers on top of+-- 'IO'.+--+-- Laws. For any value @u@ returned by 'askUnliftIO', it must meet the+-- monad transformer laws as reformulated for @MonadUnliftIO@:+--+-- * @unliftIO u . return = return@+--+-- * @unliftIO u (m >>= f) = unliftIO u m >>= unliftIO u . f@+--+-- The third is a currently nameless law which ensures that the+-- current context is preserved.+--+-- * @askUnliftIO >>= (\u -> liftIO (unliftIO u m)) = m@+--+-- If you have a name for this, please submit it in a pull request for+-- great glory.+--+-- @since 0.1.0.0+class MonadIO m => MonadUnliftIO m where+  -- | Capture the current monadic context, providing the ability to+  -- run monadic actions in 'IO'.+  --+  -- See 'UnliftIO' for an explanation of why we need a helper+  -- datatype here.+  -- @since 0.1.0.0+  askUnliftIO :: m (UnliftIO m)+  -- Would be better, but GHC hates us+  -- askUnliftIO :: m (forall a. m a -> IO a)+instance MonadUnliftIO IO where+  askUnliftIO = return (UnliftIO id)+instance MonadUnliftIO m => MonadUnliftIO (ReaderT r m) where+  askUnliftIO = ReaderT $ \r ->+                withUnliftIO $ \u ->+                return (UnliftIO (unliftIO u . flip runReaderT r))+instance MonadUnliftIO m => MonadUnliftIO (IdentityT m) where+  askUnliftIO = IdentityT $+                withUnliftIO $ \u ->+                return (UnliftIO (unliftIO u . runIdentityT))++-- | Same ask 'askUnliftIO', but returns a monomorphic function+-- instead of a polymorphic newtype wrapper. If you only need to apply+-- the transformation on one concrete type, this function can be more+-- convenient.+--+-- @since 0.1.0.0+askRunInIO :: MonadUnliftIO m => m (m a -> IO a)+askRunInIO = liftM unliftIO askUnliftIO++-- | Convenience function for capturing the monadic context and running+-- an 'IO' action.+--+-- @since 0.1.0.0+withUnliftIO :: MonadUnliftIO m => (UnliftIO m -> IO a) -> m a+withUnliftIO inner = askUnliftIO >>= liftIO . inner++-- | Same as 'withUnliftIO', but uses a monomorphic function like+-- 'askRunInIO'.+--+-- @since 0.1.0.0+withRunInIO :: MonadUnliftIO m => ((m a -> IO a) -> IO b) -> m b+withRunInIO inner = askRunInIO >>= liftIO . inner++-- | Convert an action in @m@ to an action in @IO@.+--+-- @since 0.1.0.0+toIO :: MonadUnliftIO m => m a -> m (IO a)+toIO m = withRunInIO $ \run -> return $ run m

@@ -0,0 +1,33 @@+-- This file has been generated from package.yaml by hpack version 0.17.0.+--+-- see: https://github.com/sol/hpack++name:           unliftio-core+version:        0.1.0.0+synopsis:       The MonadUnliftIO typeclass for unlifting monads to IO+description:    Please see the README.md file for details+category:       Control+homepage:       https://github.com/fpco/monad-unlift/tree/master/unliftio-core#readme+author:         Michael Snoyman, Francesco Mazzoli+maintainer:     michael@snoyman.com+copyright:      2017 FP Complete+license:        MIT+license-file:   LICENSE+build-type:     Simple+cabal-version:  >= 1.10++extra-source-files:+    ChangeLog.md+    README.md++library+  hs-source-dirs:+      src+  build-depends:+      base >= 4.5 && < 4.11+    , transformers >= 0.2 && < 0.6+  exposed-modules:+      Control.Monad.IO.Unlift+  other-modules:+      Paths_unliftio_core+  default-language: Haskell2010