Copyright	(C) 2008-2015 Edward Kmett
License	BSD-style (see the file LICENSE)
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	provisional
Portability	portable
Safe Haskell	Safe
Language	Haskell98

Control.Comonad.Store.Pointer

Contents

The Pointer comonad
The Pointer comonad transformer

Description

The array-backed store (state-in-context/costate) comonad transformer is subject to the laws:

x = seek (pos x) x
y = pos (seek y x)
seek y x = seek y (seek z x)

Thanks go to Russell O'Connor and Daniel Peebles for their help formulating and proving the laws for this comonad transformer.

This basic version of this transformer first appeared on Dan Piponi's blog at http://blog.sigfpe.com/2008/03/comonadic-arrays.html.

Since this module relies on the non-Haskell 98 arrays package, it is located here instead of in comonad-transformers.

NB: attempting to seek or peek out of bounds will yield an error.

Synopsis

type Pointer i = PointerT i Identity
pointer :: Array i a -> i -> Pointer i a
runPointer :: Pointer i a -> (Array i a, i)
data PointerT i w a = PointerT (w (Array i a)) i
runPointerT :: PointerT i w a -> (w (Array i a), i)
pointerBounds :: (Comonad w, Ix i) => PointerT i w a -> (i, i)
module Control.Comonad.Store.Class

The Pointer comonad

type Pointer i = PointerT i Identity Source #

pointer :: Array i a -> i -> Pointer i a Source #

runPointer :: Pointer i a -> (Array i a, i) Source #

The Pointer comonad transformer

data PointerT i w a Source #

Constructors

PointerT (w (Array i a)) i

Instances

(ComonadEnv m w, Ix i) => ComonadEnv m (PointerT i w) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods ask :: PointerT i w a -> m #
(Comonad w, Ix i) => ComonadStore i (PointerT i w) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods pos :: PointerT i w a -> i # peek :: i -> PointerT i w a -> a # peeks :: (i -> i) -> PointerT i w a -> a # seek :: i -> PointerT i w a -> PointerT i w a # seeks :: (i -> i) -> PointerT i w a -> PointerT i w a # experiment :: Functor f => (i -> f i) -> PointerT i w a -> f a #
(ComonadTraced m w, Ix i) => ComonadTraced m (PointerT i w) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods trace :: m -> PointerT i w a -> a #
Ix i => ComonadTrans (PointerT i) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods lower :: Comonad w => PointerT i w a -> w a #
Ix i => ComonadHoist (PointerT i) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods cohoist :: (Comonad w, Comonad v) => (forall x. w x -> v x) -> PointerT i w a -> PointerT i v a #
(Functor w, Ix i) => Functor (PointerT i w) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods fmap :: (a -> b) -> PointerT i w a -> PointerT i w b # (<$) :: a -> PointerT i w b -> PointerT i w a #
(Comonad w, Ix i) => Comonad (PointerT i w) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods extract :: PointerT i w a -> a # duplicate :: PointerT i w a -> PointerT i w (PointerT i w a) # extend :: (PointerT i w a -> b) -> PointerT i w a -> PointerT i w b #
(Comonad w, Ix i) => Extend (PointerT i w) Source #
Instance details Defined in Control.Comonad.Store.Pointer Methods duplicated :: PointerT i w a -> PointerT i w (PointerT i w a) # extended :: (PointerT i w a -> b) -> PointerT i w a -> PointerT i w b #

runPointerT :: PointerT i w a -> (w (Array i a), i) Source #

pointerBounds :: (Comonad w, Ix i) => PointerT i w a -> (i, i) Source #

Extract the bounds of the currently focused array

module Control.Comonad.Store.Class