Generic.Data.Function.FoldMap

foldMap for generic data types.

foldMap can be considered a two-step process:

• map every element a of a t a (where Foldable t) to some Monoid m
• combine elements using (<>)

Applying this to generic data types:

• map every field of a constructor to some Monoid m
• combine elements using (<>)

Field mappings are handled using a per-monoid type class. You need a monoid m with an associated type class which has a function a -> m. Write a GenericFoldMap instance for your monoid which points to your type class. If a field type doesn't have a matching instance, the generic instance emits a type error.

Sum types (with multiple constructors) are handled by (<>)-ing the constructor with its contents (in that order). You must provide a String -> m function for mapping constructor names. If you need custom sum type handling, you may write your own and still leverage the individual constructor generics.

This function can provide generic support for simple fold-y operations like serialization.

Documentation

class GenericFoldMap m where

Monoids that can be generically foldMapped to.

Associated Types

type GenericFoldMapC m a :: Constraint

The type class that enables mapping permitted types to the monoid.

The type class should provide a function that looks like genericFoldMapF.

Methods

genericFoldMapF :: GenericFoldMapC m a => a -> m

The "map" function in foldMap (first argument).

Instances

GenericFoldMap Showly

Defined in Generic.Data.Function.Example

Associated Types

type GenericFoldMapC Showly a

Methods

genericFoldMapF :: GenericFoldMapC Showly a => a -> Showly

Monoid m => GenericFoldMap (EmptyRec0 m)

foldMap over types where all fields map to mempty.

Defined in Generic.Data.Function.FoldMap.Constructor

Associated Types

type GenericFoldMapC (EmptyRec0 m) a

Methods

genericFoldMapF :: GenericFoldMapC (EmptyRec0 m) a => a -> EmptyRec0 m

GenericFoldMap (NoRec0 m)

foldMap over types with no fields in any constructor.

Defined in Generic.Data.Function.FoldMap.Constructor

Associated Types

type GenericFoldMapC (NoRec0 m) a

Methods

genericFoldMapF :: GenericFoldMapC (NoRec0 m) a => a -> NoRec0 m

genericFoldMapNonSum :: forall {cd} {f} asserts m a. (Generic a, Rep a ~ D1 cd f, GFoldMapNonSum m f, ApplyGCAsserts asserts f) => a -> m

Generic foldMap over a term of non-sum data type a.

a must have exactly one constructor.

class GFoldMapNonSum m f

foldMap over generic product data types.

Take a generic representation, map each field in the data type to a Monoid, and combine the results with (<>).

Minimal complete definition

gFoldMapNonSum

Instances

GFoldMapNonSum m (V1 :: k -> Type)

Defined in Generic.Data.Function.FoldMap.NonSum

Methods

gFoldMapNonSum :: forall (p :: k0). V1 p -> m

GFoldMapNonSum m (l :+: r :: k -> Type)

Defined in Generic.Data.Function.FoldMap.NonSum

Methods

gFoldMapNonSum :: forall (p :: k0). (l :+: r) p -> m

GFoldMapC m f => GFoldMapNonSum m (C1 c f :: k -> Type)

Defined in Generic.Data.Function.FoldMap.NonSum

Methods

gFoldMapNonSum :: forall (p :: k0). C1 c f p -> m

genericFoldMapSum :: forall {cd} {f} opts asserts m a. (Generic a, Rep a ~ D1 cd f, GFoldMapSum opts m f, ApplyGCAsserts asserts f) => (String -> m) -> a -> m

Generic foldMap over a term of sum data type a.

You must provide a function for mapping constructor names to monoidal values.

This is the most generic option, but depending on your string manipulation may be slower.

class GFoldMapSum (opts :: SumOpts) m f

Minimal complete definition

gFoldMapSum

Instances

GFoldMapSum opts m (V1 :: k -> Type)

Defined in Generic.Data.Function.FoldMap.Sum

Methods

gFoldMapSum :: forall (p :: k0). (String -> m) -> V1 p -> m

GFoldMapCSum m (C1 c f) => GFoldMapSum 'AllowSingletonSum m (C1 c f :: k -> Type)

Defined in Generic.Data.Function.FoldMap.Sum

Methods

gFoldMapSum :: forall (p :: k0). (String -> m) -> C1 c f p -> m

GFoldMapSum 'SumOnly m (C1 c f :: k -> Type)

Defined in Generic.Data.Function.FoldMap.Sum

Methods

gFoldMapSum :: forall (p :: k0). (String -> m) -> C1 c f p -> m

GFoldMapCSum m (l :+: r) => GFoldMapSum opts m (l :+: r :: k -> Type)

Defined in Generic.Data.Function.FoldMap.Sum

Methods

gFoldMapSum :: forall (p :: k0). (String -> m) -> (l :+: r) p -> m

genericFoldMapSumConsByte :: forall m a. (Generic a, GFoldMapSumConsByte m (Rep a)) => (Word8 -> m) -> a -> m

Generic foldMap over a term of sum data type a where constructors are mapped to their index (distance from first/leftmost constructor)

a must have at least two constructors.

You must provide a function for mapping bytes to monoidal values.

This should be fairly fast, but sadly I think it's slower than the generics in store and binary/cereal libraries.

class GFoldMapSumConsByte m f

Minimal complete definition

gFoldMapSumConsByte

Instances

GFoldMapSumConsByte m (V1 :: k -> Type)

Defined in Generic.Data.Function.FoldMap.SumConsByte

Methods

gFoldMapSumConsByte :: forall (p :: k0). (Word8 -> m) -> V1 p -> m

(FitsInByte (SumArity (l :+: r)), GFoldMapCSumCtrArityByte m 0 (l :+: r), GFoldMapCSumCtr m (l :+: r), Semigroup m) => GFoldMapSumConsByte m (l :+: r :: Type -> Type)

Defined in Generic.Data.Function.FoldMap.SumConsByte

Methods

gFoldMapSumConsByte :: forall (p :: k). (Word8 -> m) -> (l :+: r) p -> m

GFoldMapSumConsByte m (C1 c f :: k -> Type)

Defined in Generic.Data.Function.FoldMap.SumConsByte

Methods

gFoldMapSumConsByte :: forall (p :: k0). (Word8 -> m) -> C1 c f p -> m

GFoldMapSumConsByte m f => GFoldMapSumConsByte m (D1 c f :: k -> Type)

Defined in Generic.Data.Function.FoldMap.SumConsByte

Methods

gFoldMapSumConsByte :: forall (p :: k0). (Word8 -> m) -> D1 c f p -> m