Copyright	(c) 2016 Peter Trško
License	BSD3
Maintainer	peter.trsko@gmail.com
Stability	experimental
Portability	DataKinds, FlexibleInstances, FunctionalDependencies, MagicHash, MultiParamTypeClasses, NoImplicitPrelude, TypeFamilies, UndecidableInstances
Safe Haskell	None
Language	Haskell2010

Data.OverloadedRecords

Contents

Oveloaded Labels
Overloaded Record Fields
Orphan instances

Description

Magic classes for OverloadedRecordFields.

Implementation is based on: https://github.com/adamgundry/records-prototype/blob/master/CoherentPrototype.hs by Adam Gundry under MIT License.

Synopsis

Oveloaded Labels

module Data.OverloadedLabels

Overloaded Record Fields

Getter

type family FieldType (l :: Symbol) (s :: *) :: * Source #

When accessing field named l :: Symbol of a record s :: *, then the type of the value in that field is FieldType l s.

Instances

type FieldType "fieldDerivation" DeriveOverloadedRecordsParams Source #
type FieldType "fieldDerivation" DeriveOverloadedRecordsParams = FieldDerivation

class HasField l s a | l s -> a where Source #

Definition of this class is based on: https://phabricator.haskell.org/D1687

Minimal complete definition

getField

Methods

getField :: Proxy# l -> s -> a Source #

Get value of a field.

Instances

HasField "fieldDerivation" DeriveOverloadedRecordsParams FieldDerivation Source #
Methods getField :: Proxy# Symbol "fieldDerivation" -> DeriveOverloadedRecordsParams -> FieldDerivation Source #

Setter

type family UpdateType (l :: Symbol) (s :: *) (a :: *) :: * Source #

If field l :: Symbol of a record s :: * is set to new value which has type a :: *, then the modified record will have type UpdateType l s a.

Instances

type UpdateType "fieldDerivation" DeriveOverloadedRecordsParams FieldDerivation Source #
type UpdateType "fieldDerivation" DeriveOverloadedRecordsParams FieldDerivation = DeriveOverloadedRecordsParams

class (HasField l s b, FieldType l s ~ b) => SetField l s b where Source #

Minimal complete definition

setField

Methods

setField :: Proxy# l -> s -> b -> UpdateType l s b Source #

Set value of a field.

Instances

SetField "fieldDerivation" DeriveOverloadedRecordsParams FieldDerivation Source #
Methods setField :: Proxy# Symbol "fieldDerivation" -> DeriveOverloadedRecordsParams -> FieldDerivation -> UpdateType "fieldDerivation" DeriveOverloadedRecordsParams FieldDerivation Source #

data Setter s t b Source #

Wrapper for a set function, lens naming convention is used for type variables. Its instance for IsLabel forces overloaded label to behave as a setter.

Instances

(SetField l s b, (~) * (UpdateType l s b) t) => IsLabel l (Setter s t b) Source #
Methods fromLabel :: Proxy# Symbol l -> Setter s t b #

set :: Setter s t b -> s -> b -> t Source #

Extract set function from Setter. Using Setter instance for IsLabel forces overloaded label to behave as a setter.

Usage example:

newtype Bar a = Bar {_bar :: a}
  deriving Show

overloadedRecord ''Bar

>>> set bar (Bar (Just False)) Nothing
Bar {_bar = Nothing}

IsLabel For Getter and Lens

type family FromArrow (a :: *) :: Bool where ... Source #

Returns True if type a is a function.

Equations

FromArrow (x -> y) = True
FromArrow t = False

class z ~ FromArrow x => IsFieldAccessor l x y z | l y -> x where Source #

Distinguish between getter and lens.

Minimal complete definition

fieldAccessor

Methods

fieldAccessor :: Proxy# l -> x -> y Source #

Instances

(HasField l s a, (~) * (FieldType l s) a, (~) Bool (FromArrow s) False) => IsFieldAccessor l s a False Source #	Overloaded getter: `Proxy#` l -> r -> a
Methods fieldAccessor :: Proxy# Symbol l -> s -> a Source #
(Functor f, HasField l s a, SetField l s b, (~) * (FieldType l s) a, (~) * (UpdateType l s b) t) => IsFieldAccessor l (a -> f b) (s -> f t) True Source #	Overloaded lens: `Functor` f => `Proxy#` l -> (a -> f b) -> s -> f t
Methods fieldAccessor :: Proxy# Symbol l -> (a -> f b) -> s -> f t Source #

Orphan instances

IsFieldAccessor l x y (FromArrow x) => IsLabel l (x -> y) Source #
Methods fromLabel :: Proxy# Symbol l -> x -> y #