| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Effectful.Dispatch.Static.Primitive
Description
Primitive API for statically dispatched effects.
This module exposes internal implementation details of the Eff
monad. Most of the time functions from Effectful.Dispatch.Static are
sufficient.
Warning: playing the so called "type tetris" with functions from this module is not enough. Their misuse might lead to memory corruption or segmentation faults, so make sure you understand what you're doing.
Synopsis
- data Env (es :: [Effect])
- newtype Relinker :: (Effect -> Type) -> Effect -> Type where
- dummyRelinker :: Relinker rep e
- type family EffectRep (d :: Dispatch) :: Effect -> Type
- consEnv :: EffectRep (DispatchOf e) e -> Relinker (EffectRep (DispatchOf e)) e -> Env es -> IO (Env (e ': es))
- unconsEnv :: Env (e ': es) -> IO ()
- getEnv :: forall e es. e :> es => Env es -> IO (EffectRep (DispatchOf e) e)
- putEnv :: forall e es. e :> es => Env es -> EffectRep (DispatchOf e) e -> IO ()
- stateEnv :: forall e es a. e :> es => Env es -> (EffectRep (DispatchOf e) e -> (a, EffectRep (DispatchOf e) e)) -> IO a
- modifyEnv :: forall e es. e :> es => Env es -> (EffectRep (DispatchOf e) e -> EffectRep (DispatchOf e) e) -> IO ()
- emptyEnv :: IO (Env '[])
- cloneEnv :: Env es -> IO (Env es)
- forkEnv :: Env es -> IO (Env es)
- sizeEnv :: Env es -> IO Int
- checkSizeEnv :: Env es -> IO ()
- tailEnv :: Env (e ': es) -> IO (Env es)
The environment
data Env (es :: [Effect]) Source #
A strict (WHNF), thread local, mutable, extensible record indexed by types
of kind Effect.
Supports forking, i.e. introduction of local branches for encapsulation of effects specific to effect handlers.
Warning: the environment is a mutable data structure and cannot be simultaneously used from multiple threads under any circumstances.
In order to pass it to a different thread, you need to perform a deep copy
with the cloneEnv funtion.
Offers very good performance characteristics for most often performed operations:
- Extending:
O(1)(amortized). - Shrinking:
O(1). - Indexing via
(:>):O(1) - Modification of a specific element:
O(1). - Forking:
O(n), wherenis the size of the effect stack. - Cloning:
O(N + Σ(n_i)), whereNis the size of theStorage, whileiranges over handlers of dynamically dispatched effects in theStorageandn_iis the size of the effect stack ofi-th handler.
Relinker
newtype Relinker :: (Effect -> Type) -> Effect -> Type where Source #
A function for relinking Env objects stored in the handlers and/or making
a deep copy of the representation of the effect when cloning the environment.
dummyRelinker :: Relinker rep e Source #
A dummy Relinker.
Representation of effects
type family EffectRep (d :: Dispatch) :: Effect -> Type Source #
Internal representations of effects.
Extending and shrinking
Arguments
| :: EffectRep (DispatchOf e) e | The representation of the effect. |
| -> Relinker (EffectRep (DispatchOf e)) e | |
| -> Env es | |
| -> IO (Env (e ': es)) |
Extend the environment with a new data type (in place).
unconsEnv :: Env (e ': es) -> IO () Source #
Shrink the environment by one data type (in place).
Note: after calling this function the input environment is no longer usable.
Data retrieval and update
Arguments
| :: forall e es. e :> es | |
| => Env es | The environment. |
| -> IO (EffectRep (DispatchOf e) e) |
Extract a specific data type from the environment.
Arguments
| :: forall e es. e :> es | |
| => Env es | The environment. |
| -> EffectRep (DispatchOf e) e | |
| -> IO () |
Replace the data type in the environment with a new value (in place).
Arguments
| :: forall e es a. e :> es | |
| => Env es | The environment. |
| -> (EffectRep (DispatchOf e) e -> (a, EffectRep (DispatchOf e) e)) | |
| -> IO a |
Modify the data type in the environment (in place) and return a value.
Arguments
| :: forall e es. e :> es | |
| => Env es | The environment. |
| -> (EffectRep (DispatchOf e) e -> EffectRep (DispatchOf e) e) | |
| -> IO () |
Modify the data type in the environment (in place).
Utils
forkEnv :: Env es -> IO (Env es) Source #
Create a fork of the environment.
Forked environment can be updated independently of the original one within the same thread.
checkSizeEnv :: Env es -> IO () Source #
Check that the size of the environment is internally consistent.