Safe Haskell | None |
---|---|

Language | Haskell2010 |

## Synopsis

- type FreerT f = FreeT (Ap f)
- type Fraxl r = FreerT (Union r)
- type Fetch f m a = ASeq f a -> m (ASeq m a)
- runFraxl :: Monad m => (forall a'. Fetch f m a') -> FreerT f m a -> m a
- simpleAsyncFetch :: MonadIO m => (forall x. f x -> IO x) -> Fetch f m a
- fetchNil :: Applicative m => Fetch (Union '[]) m a
- (|:|) :: forall f r a m. Monad m => (forall a'. Fetch f m a') -> (forall a'. Fetch (Union r) m a') -> Fetch (Union (f ': r)) m a
- hoistFetch :: Functor m => (forall x. m x -> n x) -> Fetch f m a -> Fetch f n a
- transFetch :: (forall x. g x -> f x) -> Fetch f m a -> Fetch g m a
- data ASeq (f :: Type -> Type) a where
- reduceASeq :: Applicative f => ASeq f u -> f u
- hoistASeq :: (forall x. f x -> g x) -> ASeq f a -> ASeq g a
- traverseASeq :: Applicative h => (forall x. f x -> h (g x)) -> ASeq f a -> h (ASeq g a)
- rebaseASeq :: ASeq f u -> (forall x. (x -> y) -> ASeq f x -> z) -> (v -> u -> y) -> ASeq f v -> z
- newtype CachedFetch f a = CachedFetch (f a)
- fetchCached :: forall t m f a. (Monad m, MonadTrans t, MonadState (DMap f MVar) (t m), GCompare f, MonadIO (t m)) => (forall a'. Fetch f m a') -> Fetch (CachedFetch f) (t m) a
- runCachedFraxl :: forall m f a. (MonadIO m, GCompare f) => (forall a'. Fetch f m a') -> FreerT f m a -> DMap f MVar -> m (a, DMap f MVar)
- evalCachedFraxl :: forall m f a. (MonadIO m, GCompare f) => (forall a'. Fetch f m a') -> FreerT f m a -> m a
- module Data.GADT.Compare
- newtype Union ts f = Union (Sum ts f)
- unconsCoRec :: Sum (t ': ts) f -> Either (t f) (Sum ts f)

# The Fraxl Monad

type FreerT f = FreeT (Ap f) Source #

Fraxl is based on a particular Freer monad. This Freer monad has applicative optimization, which is used to parallelize effects.

type Fetch f m a = ASeq f a -> m (ASeq m a) Source #

A data source is an effect `f`

that operates in some monad `m`

.
Given a sequence of effects,
a data source should use `m`

to prepare a corresponding sequence of results.

fetchNil :: Applicative m => Fetch (Union '[]) m a Source #

Fetch empty union.
Only necessary to terminate a list of `Fetch`

functions for `Fetch (Union r)`

(|:|) :: forall f r a m. Monad m => (forall a'. Fetch f m a') -> (forall a'. Fetch (Union r) m a') -> Fetch (Union (f ': r)) m a infixr 5 Source #

Like '(:)' for constructing `Fetch (Union (f ': r))`

hoistFetch :: Functor m => (forall x. m x -> n x) -> Fetch f m a -> Fetch f n a Source #

Hoist a `Fetch`

function into a different result monad.

transFetch :: (forall x. g x -> f x) -> Fetch f m a -> Fetch g m a Source #

Translate a `Fetch`

function from `f`

requests, to `g`

requests.

# The Sequence of Effects

data ASeq (f :: Type -> Type) a where #

The free applicative is composed of a sequence of effects,
and a pure function to apply that sequence to.
The fast free applicative separates these from each other,
so that the sequence may be built up independently,
and so that `fmap`

can run in constant time by having immediate access to the pure function.

reduceASeq :: Applicative f => ASeq f u -> f u #

hoistASeq :: (forall x. f x -> g x) -> ASeq f a -> ASeq g a #

Given a natural transformation from `f`

to `g`

this gives a natural transformation from `ASeq f`

to `ASeq g`

.

traverseASeq :: Applicative h => (forall x. f x -> h (g x)) -> ASeq f a -> h (ASeq g a) #

Traverse a sequence with resepect to its interpretation type `f`

.

rebaseASeq :: ASeq f u -> (forall x. (x -> y) -> ASeq f x -> z) -> (v -> u -> y) -> ASeq f v -> z #

It may not be obvious, but this essentially acts like ++, traversing the first sequence and creating a new one by appending the second sequence. The difference is that this also has to modify the return functions and that the return type depends on the input types.

See the source of `hoistAp`

as an example usage.

# Caching

newtype CachedFetch f a Source #

Caching in Fraxl works by translating `FreerT f`

into
`FreerT (CachedFetch f)`

, then running with `CachedFetch'`

s DataSource.
That instance requires `f`

to to have a `GCompare`

instance.

The `CachedFetch`

instance uses a `MonadState`

to track cached requests.
The state variable is a `DMap`

from the 'dependent-map' package.
Keys are requests, and values are `MVar`

s of the results.

CachedFetch (f a) |

fetchCached :: forall t m f a. (Monad m, MonadTrans t, MonadState (DMap f MVar) (t m), GCompare f, MonadIO (t m)) => (forall a'. Fetch f m a') -> Fetch (CachedFetch f) (t m) a Source #

runCachedFraxl :: forall m f a. (MonadIO m, GCompare f) => (forall a'. Fetch f m a') -> FreerT f m a -> DMap f MVar -> m (a, DMap f MVar) Source #

Runs a Fraxl computation with caching using a given starting cache. Alongside the result, it returns the final cache.

evalCachedFraxl :: forall m f a. (MonadIO m, GCompare f) => (forall a'. Fetch f m a') -> FreerT f m a -> m a Source #

Like `runCachedFraxl`

, except it starts with an empty cache
and discards the final cache.

module Data.GADT.Compare

# Union

`Union`

represents a value of any type constructor in `r`

applied with `a`

.

## Instances

(Monad m, KnownNat (ElemIndex f r)) => MonadFraxl f (Fraxl r m) Source # | |

Defined in Control.Monad.Fraxl.Class | |

(GCompare f, GCompare (Union r)) => GCompare (Union (f ': r) :: Type -> Type) Source # | |

GCompare (Union ([] :: [Type -> Type])) Source # | |

(GEq f, GEq (Union r)) => GEq (Union (f ': r) :: Type -> Type) Source # | |

GEq (Union ([] :: [Type -> Type])) Source # | |