Copyright	(c) 2023 Sayo Koyoneda
License	MPL-2.0 (see the file LICENSE)
Maintainer	[email protected]
Safe Haskell	None
Language	GHC2021

Data.Effect.Writer

Description

Effects that can accumulate values monoidally in a context.

Synopsis

data Tell w a where
- Tell :: forall w. w -> Tell w ()
data WriterH w (f :: Type -> Type) a where
- Listen :: forall (f :: Type -> Type) a1 w. f a1 -> WriterH w f (w, a1)
- Censor :: forall w (f :: Type -> Type) a. (w -> w) -> f a -> WriterH w f a
type LTell w = LiftFOE (Tell w)
pattern LTell :: forall a w f. () => (a ~ (), ()) => w -> LiftFOE (Tell w) f a
tell :: SendFOE (Tell w) f => w -> f ()
tell' :: forall {k} (tag :: k) w f. SendFOE (Tag (Tell w) tag) f => w -> f ()
tell'' :: forall {k} (key :: k) w f. SendFOEBy key (Tell w) f => w -> f ()
listen :: forall a w f. SendHOE (WriterH w) f => f a -> f (w, a)
listen' :: forall {k} (tag :: k) a w f. SendHOE (TagH (WriterH w) tag) f => f a -> f (w, a)
listen'' :: forall {k} (key :: k) a w f. SendHOEBy key (WriterH w) f => f a -> f (w, a)
censor :: forall w a f. SendHOE (WriterH w) f => (w -> w) -> f a -> f a
censor' :: forall {k} (tag :: k) w a f. SendHOE (TagH (WriterH w) tag) f => (w -> w) -> f a -> f a
censor'' :: forall {k} (key :: k) w a f. SendHOEBy key (WriterH w) f => (w -> w) -> f a -> f a
pass :: (Tell w <: m, WriterH w <<: m, Monad m) => m (w -> w, a) -> m a

Documentation

data Tell w a where Source #

An effect that can accumulate values monoidally in a context.

Constructors

Tell :: forall w. w -> Tell w ()

Accumulates new values to the cumulative value held in the context.

data WriterH w (f :: Type -> Type) a where Source #

An effect that performs local operations on accumulations in the context on a per-scope basis.

Constructors

Listen	Obtains the accumulated value in the scope and returns it together as a pair.
Fields :: forall (f :: Type -> Type) a1 w. f a1 The scope from which to obtain the accumulation. -> WriterH w f (w, a1)
Censor	Modifies the accumulation in the scope based on the given function.
Fields :: forall w (f :: Type -> Type) a. (w -> w) A function for modifying the accumulated value. -> f a The scope where the modification is applied. -> WriterH w f a

Instances

Instances details

() => HFunctor (WriterH w) Source #
Instance details Defined in Data.Effect.Writer Methods hfmap :: forall (f :: Type -> Type) (g :: Type -> Type). (f :-> g) -> WriterH w f :-> WriterH w g #

type LTell w = LiftFOE (Tell w) Source #

pattern LTell :: forall a w f. () => (a ~ (), ()) => w -> LiftFOE (Tell w) f a Source #

tell :: SendFOE (Tell w) f => w -> f () Source #

Accumulates new values to the cumulative value held in the context.

tell' :: forall {k} (tag :: k) w f. SendFOE (Tag (Tell w) tag) f => w -> f () Source #

Accumulates new values to the cumulative value held in the context.

tell'' :: forall {k} (key :: k) w f. SendFOEBy key (Tell w) f => w -> f () Source #

Accumulates new values to the cumulative value held in the context.

listen Source #

Arguments

:: forall a w f. SendHOE (WriterH w) f
=> f a	The scope from which to obtain the accumulation.
-> f (w, a)

Obtains the accumulated value in the scope and returns it together as a pair.

listen' Source #

Arguments

:: forall {k} (tag :: k) a w f. SendHOE (TagH (WriterH w) tag) f
=> f a	The scope from which to obtain the accumulation.
-> f (w, a)

Obtains the accumulated value in the scope and returns it together as a pair.

listen'' Source #

Arguments

:: forall {k} (key :: k) a w f. SendHOEBy key (WriterH w) f
=> f a	The scope from which to obtain the accumulation.
-> f (w, a)

Obtains the accumulated value in the scope and returns it together as a pair.

censor Source #

Arguments

:: forall w a f. SendHOE (WriterH w) f
=> (w -> w)
-> f a	The scope where the modification is applied.
-> f a

Modifies the accumulation in the scope based on the given function.

censor' Source #

Arguments

:: forall {k} (tag :: k) w a f. SendHOE (TagH (WriterH w) tag) f
=> (w -> w)
-> f a	The scope where the modification is applied.
-> f a

Modifies the accumulation in the scope based on the given function.

censor'' Source #

Arguments

:: forall {k} (key :: k) w a f. SendHOEBy key (WriterH w) f
=> (w -> w)
-> f a	The scope where the modification is applied.
-> f a

Modifies the accumulation in the scope based on the given function.

pass :: (Tell w <: m, WriterH w <<: m, Monad m) => m (w -> w, a) -> m a Source #

For a given scope, uses the function (the first component of the pair returned by that scope) to modify the accumulated value of that scope, and then accumulates the result into the current outer scope.

pass m = do
    (w, (f, a)) <- listen m
    tell $ f w
    pure a