Safe Haskell	Safe-Inferred
Language	GHC2021

Generic.Data.Function.Traverse

Description

traverse for generic data types.

TODO This is harder to conceptualize than generic foldMap. No nice clean explanation yet.

This function can provide generic support for simple parser-esque types.

Synopsis

class GenericTraverse f where
- type GenericTraverseC f a :: Constraint
- genericTraverseAction :: GenericTraverseC f a => String -> String -> Maybe String -> Natural -> f a
genericTraverseNonSum :: forall f a. (Generic a, GTraverseNonSum f (Rep a), Functor f) => f a
class GTraverseNonSum f f'
class (GenericTraverse f, Alternative f, Monad f) => GenericTraverseSum f where
- genericTraverseSumPfxTagAction :: GenericTraverseC f pt => String -> f pt
- genericTraverseSumNoMatchingCstrAction :: String -> [String] -> Text -> f a
data PfxTagCfg a = PfxTagCfg {
- pfxTagCfgFromCstr :: String -> a
- pfxTagCfgEq :: a -> a -> Bool
- pfxTagCfgShow :: a -> Text
}
genericTraverseSum :: forall f a pt. (Generic a, GTraverseSum f (Rep a), GenericTraverseC f pt, Functor f) => PfxTagCfg pt -> f a
class GTraverseSum f f'
eqShowPfxTagCfg :: (Eq a, Show a) => (String -> a) -> PfxTagCfg a

Documentation

class GenericTraverse f where Source #

Applicative functors that can be generically traversed.

Associated Types

type GenericTraverseC f a :: Constraint Source #

The type class providing (applicative) actions for permitted types.

Methods

genericTraverseAction Source #

Arguments

:: GenericTraverseC f a
=> String	data type name
-> String	constructor name
-> Maybe String	record name (if present)
-> Natural	field index
-> f a

The action in traverse (first argument).

We include data type metadata because this function is useful for monadic parsers, which can record it in error messages. (We don't do it for foldMap because it's pure.)

Instances

Instances details

GenericTraverse EmptyRec0 Source #	`traverse` over types where all fields map to their respective `mempty`. Can result in type errors lacking context: a field missing a `Monoid` instance will type error with a regular "no instance for" message, without telling you the surrounding type. Maybe silly.
Instance details Defined in Generic.Data.Function.Traverse.Constructor Associated Types type GenericTraverseC EmptyRec0 a Source # Methods genericTraverseAction :: GenericTraverseC EmptyRec0 a => String -> String -> Maybe String -> Natural -> EmptyRec0 a Source #
GenericTraverse NoRec0 Source #	`traverse` over types with no fields in any constructor.
Instance details Defined in Generic.Data.Function.Traverse.Constructor Associated Types type GenericTraverseC NoRec0 a Source # Methods genericTraverseAction :: GenericTraverseC NoRec0 a => String -> String -> Maybe String -> Natural -> NoRec0 a Source #

genericTraverseNonSum :: forall f a. (Generic a, GTraverseNonSum f (Rep a), Functor f) => f a Source #

Generic traverse over a term of non-sum data type f a.

f a must have exactly one constructor.

class GTraverseNonSum f f' Source #

Minimal complete definition

gTraverseNonSum

Instances

Instances details

(Functor f, GTraverseNonSum' cd f f') => GTraverseNonSum (f :: Type -> Type) (D1 cd f' :: k -> Type) Source #
Instance details Defined in Generic.Data.Function.Traverse.NonSum Methods gTraverseNonSum :: forall (p :: k0). f (D1 cd f' p) Source #

class (GenericTraverse f, Alternative f, Monad f) => GenericTraverseSum f where Source #

Sum type monads that can be generically traversed.

For sum types, we require a monad with choice to differentiate constructors.

Methods

genericTraverseSumPfxTagAction Source #

Arguments

:: GenericTraverseC f pt
=> String	data type name
-> f pt

Try to parse a prefix tag of type pt.

Relevant metadata is provided as arguments.

genericTraverseSumNoMatchingCstrAction Source #

Arguments

:: String	data type name
-> [String]	non-matching constructor names
-> Text	prefix tag, prettified
-> f a

Parse error due to no constructor matching the parsed prefix tag.

Relevant metadata is provided as arguments.

data PfxTagCfg a Source #

How to use a type as a prefix tag in a generic sum type parser.

Constructors

PfxTagCfg

Fields

pfxTagCfgFromCstr :: String -> a
How to turn a constructor name into a prefix tag.
pfxTagCfgEq :: a -> a -> Bool
How to compare prefix tags for equality.
By shoving this into our generic derivation config, we can avoid adding an insidious Eq constraint. In general, you will want to set this to (==).
pfxTagCfgShow :: a -> Text
Make a prefix tag human-readable. show is often appropriate.

genericTraverseSum :: forall f a pt. (Generic a, GTraverseSum f (Rep a), GenericTraverseC f pt, Functor f) => PfxTagCfg pt -> f a Source #

Generic traverse over a term of sum data type f a.

f a must have at least two constructors.

You must provide a configuration for how to handle constructors.

class GTraverseSum f f' Source #

Minimal complete definition

gTraverseSum

Instances

Instances details

(Functor f, GTraverseSum' cd f f') => GTraverseSum f (D1 cd f' :: k -> Type) Source #
Instance details Defined in Generic.Data.Function.Traverse.Sum Methods gTraverseSum :: forall pt (p :: k0). GenericTraverseC f pt => PfxTagCfg pt -> f (D1 cd f' p) Source #

eqShowPfxTagCfg :: (Eq a, Show a) => (String -> a) -> PfxTagCfg a Source #

Construct a prefix tag config using existing Eq and Show instances.

The user only needs to provide the constructor name parser.