polysemy-keyed-state: Effect for a set of stateful values indexed by a type of keys
The KeyedState k effect provides access to a set of stateful values indexed by some key type k :: Type -> Type, where a key of type k a can be used to access a stateful value of type a.
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| Versions [RSS] | 0.1, 0.1.1 |
|---|---|
| Change log | CHANGELOG.md |
| Dependencies | base (>=4.12 && <4.15), constraints (>=0.11 && <0.14), constraints-extras (>=0.3.0.2 && <0.4), polysemy (>=1.3 && <1.6), some (>=1.0.1 && <1.1), StateVar (>=1.2 && <1.3), trivial-constraint (>=0.3 && <0.8) [details] |
| License | BSD-3-Clause |
| Author | |
| Maintainer | Katie Casamento <kcsmnt0@gmail.com> |
| Category | BSD3, Library |
| Home page | https://github.com/kcsmnt0/polysemy-keyed-state#readme |
| Bug tracker | https://github.com/kcsmnt0/polysemy-keyed-state/issues |
| Source repo | head: git clone https://github.com/kcsmnt0/polysemy-keyed-state |
| Uploaded | by kcsmnt0 at 2021-07-13T21:54:29Z |
| Distributions | |
| Downloads | 270 total (11 in the last 30 days) |
| Rating | (no votes yet) [estimated by Bayesian average] |
| Your Rating | |
| Status | Docs available [build log] Last success reported on 2021-07-13 [all 1 reports] |
Readme for polysemy-keyed-state-0.1.1
[back to package description]polysemy-keyed-state
This package provides the KeyedState effect for use with polysemy. For any key type k :: Type -> Type, the KeyedState k effect provides access to a set of stateful values indexed by k, where a key of type k a can be used to access a stateful value of type a.
In the most direct use case, the KeyedState effect can be used as an interface to low-level reference types like IORef and STRef: for example, getAt can be used with the type Member (KeyedState IORef) r => IORef a -> Sem r a.
At a higher level, key types defined as GADTs can be used with KeyedState to represent sets of stateful variables in a single effect. For example, with the GADT definition of K below, the effect KeyedState K provides access to an Int value with key X and a Bool value with key Y.
data K a where
X :: K Int
Y :: K Bool
By mapping high-level keys to low-level references, the KeyedState effect can be used to implement a high-level interface to a set of low-level variables.
Some of the interpreters for KeyedState require instances of Has for certain typeclasses, which can be generated for most GADT key types with deriveArgDict from the constraints-extras package.