use MonadBase from monad-control
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Jamie Bertram
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README.md
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README.md
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[](https://github.com/purescript/purescript-unlift/actions?query=workflow%3ACI+branch%3Amain)
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[](https://pursuit.purescript.org/packages/purescript-unlift)
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Standard library for working with monads at the base of a transformer stack.
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`MonadBase` allow any base monad to be lifted into a transformed monad à la
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`MonadEffect` and `MonadAff`. `MonadUnliftEffect`, `MonadUnliftAff`, and
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`MonadUnlift` allow running a stateless transformed monad inside of a base
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monad. Based on:
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Classes that allow stateless monads to be "unlifted" into a base monad.
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- `MonadUnliftEffect`: Run any compatible monad in `Effect`
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- `MonadUnliftAff`: Run any compatible monad in `Aff`
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- `MonadUnlift`: Run any compatible monad in any base monad.
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Based on:
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- [transformers-base](http://hackage.haskell.org/package/transformers-base)
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- [unliftio](http://hackage.haskell.org/package/unliftio)
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- [unlift](http://hackage.haskell.org/package/unlift)
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@ -23,4 +24,3 @@ spago install unlift
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## Documentation
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Module documentation is [published on Pursuit](http://pursuit.purescript.org/packages/purescript-unlift).
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@ -17,11 +17,14 @@
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"purescript-aff": "^v6.0.0",
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"purescript-effect": "^v3.0.0",
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"purescript-either": "^v5.0.0",
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"purescript-freet": "^v6.0.0",
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"purescript-identity": "^v5.0.0",
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"purescript-lists": "^v6.0.1",
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"purescript-maybe": "^v5.0.0",
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"purescript-monad-control": "^v5.0.0",
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"purescript-prelude": "^v5.0.1",
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"purescript-st": "^v5.0.1",
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"purescript-transformers": "^v5.2.0"
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"purescript-transformers": "^v5.2.0",
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"purescript-tuples": "^v6.0.1"
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}
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}
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[ "aff"
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, "effect"
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, "either"
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, "freet"
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, "identity"
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, "lists"
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, "maybe"
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, "monad-control"
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, "prelude"
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, "st"
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, "transformers"
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, "tuples"
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]
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, packages = ./packages.dhall
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, sources = [ "src/**/*.purs" ]
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@ -1,105 +0,0 @@
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module Control.Monad.Base where
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import Prelude
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import Control.Monad.Cont (ContT)
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import Control.Monad.Except (ExceptT)
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import Control.Monad.Identity.Trans (IdentityT)
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import Control.Monad.List.Trans (ListT)
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import Control.Monad.Maybe.Trans (MaybeT)
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import Control.Monad.RWS (RWST)
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import Control.Monad.Reader (ReaderT)
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import Control.Monad.ST (ST)
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import Control.Monad.State (StateT)
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import Control.Monad.Trans.Class (class MonadTrans, lift)
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import Control.Monad.Writer (WriterT)
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import Data.Either (Either)
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import Data.Identity (Identity)
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import Data.List (List)
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import Data.List.Lazy as LL
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import Data.Maybe (Maybe)
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import Effect (Effect)
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import Effect.Aff (Aff)
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-- | A class for lifting computations in a monad at the bottom of a transformer
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-- | stack.
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-- |
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-- | `MonadBase` is a generalization of the concept represented by classes like
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-- | `MonadEffect` and `MonadAff`.
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-- |
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-- | Instances should satisfy the following laws, which state that `liftBase`
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-- | is a transformer of monads:
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-- |
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-- | ```purescript
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-- | liftBase <<< pure = pure
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-- | liftBase (f =<< m) = liftBase <<< f =<< liftBase m
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-- | ```
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class (Monad b, Monad m) <= MonadBase b m | m -> b where
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-- | Lift a computation from the base monad.
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liftBase :: b ~> m
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instance MonadBase Array Array where
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liftBase = identity
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instance MonadBase List List where
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liftBase = identity
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instance MonadBase LL.List LL.List where
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liftBase = identity
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instance MonadBase Maybe Maybe where
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liftBase = identity
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instance MonadBase Effect Effect where
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liftBase = identity
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instance MonadBase Aff Aff where
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liftBase = identity
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instance MonadBase Identity Identity where
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liftBase = identity
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instance MonadBase (Either e) (Either e) where
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liftBase = identity
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instance MonadBase (ST s) (ST s) where
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liftBase = identity
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instance MonadBase (Function r) (Function r) where
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liftBase = identity
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instance MonadBase b m => MonadBase b (ListT m) where
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liftBase = liftBaseDefault
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instance MonadBase b m => MonadBase b (MaybeT m) where
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liftBase = liftBaseDefault
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instance (Monoid w, MonadBase b m) => MonadBase b (WriterT w m) where
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liftBase = liftBaseDefault
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instance MonadBase b m => MonadBase b (ExceptT e m) where
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liftBase = liftBaseDefault
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instance MonadBase b m => MonadBase b (StateT s m) where
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liftBase = liftBaseDefault
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instance MonadBase b m => MonadBase b (ReaderT r m) where
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liftBase = liftBaseDefault
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instance MonadBase b m => MonadBase b (IdentityT m) where
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liftBase = liftBaseDefault
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instance MonadBase b m => MonadBase b (ContT r m) where
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liftBase = liftBaseDefault
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instance (Monoid w, MonadBase b m) => MonadBase b (RWST r w s m) where
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liftBase = liftBaseDefault
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-- | A default implementation of `liftBase` which is defined as
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-- |
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-- | ```purescript
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-- | lift <<< liftBase
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-- | ```
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liftBaseDefault
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:: forall t m b. MonadTrans t => Monad m => MonadBase b m => b ~> t m
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liftBaseDefault = lift <<< liftBase
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@ -3,14 +3,12 @@ module Control.Monad.Unlift where
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import Prelude
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import Control.Monad.Base (class MonadBase)
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import Control.Monad.Identity.Trans (IdentityT(..))
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import Control.Monad.Reader (ReaderT(..))
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import Control.Monad.ST (ST)
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import Data.Either (Either)
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import Data.Identity (Identity)
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import Data.List (List)
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import Data.List.Lazy as LL
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import Data.Maybe (Maybe)
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import Data.Tuple (Tuple)
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import Effect (Effect)
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import Effect.Aff (Aff)
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@ -45,9 +43,6 @@ instance MonadUnlift Array Array where
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instance MonadUnlift List List where
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withRunInBase runAction = runAction identity
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instance MonadUnlift LL.List LL.List where
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withRunInBase runAction = runAction identity
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instance MonadUnlift Maybe Maybe where
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withRunInBase runAction = runAction identity
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@ -63,7 +58,7 @@ instance MonadUnlift Identity Identity where
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instance MonadUnlift (Either e) (Either e) where
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withRunInBase runAction = runAction identity
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instance MonadUnlift (ST s) (ST s) where
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instance Monoid a => MonadUnlift (Tuple a) (Tuple a) where
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withRunInBase runAction = runAction identity
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instance MonadUnlift b m => MonadUnlift b (ReaderT r m) where
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@ -72,11 +67,12 @@ instance MonadUnlift b m => MonadUnlift b (ReaderT r m) where
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runAction \(ReaderT reader) ->
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runMInBase $ reader context
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instance MonadUnlift b m => MonadUnlift b (IdentityT m) where
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withRunInBase runAction = IdentityT $
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withRunInBase \runMInBase ->
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runAction \(IdentityT a) ->
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runMInBase a
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-- TODO add MonadBase instance for IdentityT
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-- instance MonadUnlift b m => MonadUnlift b (IdentityT m) where
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-- withRunInBase runAction = IdentityT $
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-- withRunInBase \runMInBase ->
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-- runAction \(IdentityT a) ->
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-- runMInBase a
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-- | A newtype wrapper around a natural transformation from `m` to `b`.
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newtype Unlift :: forall k. (k -> Type) -> (k -> Type) -> Type
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