| Safe Haskell | Safe |
|---|---|
| Language | Haskell2010 |
Mu.Schema.Definition
Contents
Description
This module gives a set of combinators to define schemas in the sense of Avro or Protocol Buffers.
In order to re-use definitions at both
the type and term levels, the actual
constructors are defined in types ending
with B, and are parametrized by the type
used to describe identifiers.
The versions without the suffix set this
parameter to Type, and are thought as the
API to be used in the type-level.
If you use reflectSchema to obtain a term-
level representation, the parameter is set
to TypeRep.
Synopsis
- type Schema' = Schema Symbol Symbol
- type Schema typeName fieldName = SchemaB Type typeName fieldName
- type SchemaB builtin typeName fieldName = [TypeDefB builtin typeName fieldName]
- type TypeDef = TypeDefB Type
- data TypeDefB builtin typeName fieldName
- newtype ChoiceDef fieldName = ChoiceDef fieldName
- type FieldDef = FieldDefB Type
- data FieldDefB builtin typeName fieldName = FieldDef fieldName (FieldTypeB builtin typeName)
- type FieldType = FieldTypeB Type
- data FieldTypeB builtin typeName
- = TNull
- | TPrimitive builtin
- | TSchematic typeName
- | TOption (FieldTypeB builtin typeName)
- | TList (FieldTypeB builtin typeName)
- | TMap (FieldTypeB builtin typeName) (FieldTypeB builtin typeName)
- | TUnion [FieldTypeB builtin typeName]
- type family (sch :: Schema t f) :/: (name :: t) :: TypeDef t f where ...
- data Mapping a b = a :-> b
- type Mappings a b = [Mapping a b]
- type family MappingRight (ms :: Mappings a b) (v :: a) :: b where ...
- type family MappingLeft (ms :: Mappings a b) (v :: b) :: a where ...
- reflectSchema :: ReflectSchema s => Proxy s -> SchemaB TypeRep String String
- reflectFields :: ReflectFields fs => Proxy fs -> [FieldDefB TypeRep String String]
- reflectChoices :: ReflectChoices cs => Proxy cs -> [ChoiceDef String]
- reflectFieldTypes :: ReflectFieldTypes ts => Proxy ts -> [FieldTypeB TypeRep String]
- reflectFieldType :: ReflectFieldType ty => Proxy ty -> FieldTypeB TypeRep String
- class KnownName (a :: k) where
Definition of schemas
type Schema' = Schema Symbol Symbol Source #
A set of type definitions,
where the names of types and fields are
defined by type-level strings (Symbols).
type Schema typeName fieldName = SchemaB Type typeName fieldName Source #
A set of type definitions.
In general, we can use any kind we want for
both type and field names, although in practice
you always want to use Symbol.
type SchemaB builtin typeName fieldName = [TypeDefB builtin typeName fieldName] Source #
A set of type definitions, parametric on type representations.
type TypeDef = TypeDefB Type Source #
Defines a type in a schema. Each type can be: * a record: a list of key-value pairs, * an enumeration: an element of a list of choices, * a reference to a primitive type.
data TypeDefB builtin typeName fieldName Source #
Defines a type in a schema, parametric on type representations.
Constructors
| DRecord typeName [FieldDefB builtin typeName fieldName] | A list of key-value pairs. |
| DEnum typeName [ChoiceDef fieldName] | An element of a list of choices. |
| DSimple (FieldTypeB builtin typeName) | A reference to a primitive type. |
Instances
newtype ChoiceDef fieldName Source #
Defines each of the choices in an enumeration.
Constructors
| ChoiceDef fieldName | One single choice from an enumeration. |
Instances
type FieldDef = FieldDefB Type Source #
Defines a field in a record by a name and the corresponding type.
data FieldDefB builtin typeName fieldName Source #
Defines a field in a record, parametric on type representations.
Constructors
| FieldDef fieldName (FieldTypeB builtin typeName) | One single field in a record. |
Instances
type FieldType = FieldTypeB Type Source #
Types of fields of a record.
References to other types in the same schema
are done via the TSchematic constructor.
data FieldTypeB builtin typeName Source #
Types of fields of a record, parametric on type representations.
Constructors
| TNull | Null, as found in Avro. |
| TPrimitive builtin | Reference to a primitive type, such as integers or Booleans. The set of supported primitive types depends on the protocol. |
| TSchematic typeName | Reference to another type in the schema. |
| TOption (FieldTypeB builtin typeName) | Optional value. |
| TList (FieldTypeB builtin typeName) | List of values. |
| TMap (FieldTypeB builtin typeName) (FieldTypeB builtin typeName) | Map of values. The set of supported key types depends on the protocol. |
| TUnion [FieldTypeB builtin typeName] | Represents a choice between types. |
type family (sch :: Schema t f) :/: (name :: t) :: TypeDef t f where ... Source #
Lookup a type in a schema by its name.
One-to-one mappings
Finding correspondences
type family MappingRight (ms :: Mappings a b) (v :: a) :: b where ... Source #
Finds the corresponding right value of v
in a mapping ms. When the kinds are Symbol,
return the same value if not found.
When the return type is Type, return ' ()'
if the value is not found.
Equations
| MappingRight '[] (v :: Symbol) = (v :: Symbol) | |
| MappingRight '[] (v :: Symbol) = (() :: Type) | |
| MappingRight '[] v = TypeError (Text "Cannot find value " :<>: ShowType v) | |
| MappingRight ((x :-> y) ': rest) x = y | |
| MappingRight (other ': rest) x = MappingRight rest x |
type family MappingLeft (ms :: Mappings a b) (v :: b) :: a where ... Source #
Finds the corresponding left value of v
in a mapping ms. When the kinds are Symbol,
return the same value if not found.
When the return type is Type, return ' ()'
if the value is not found.
Equations
| MappingLeft '[] (v :: Symbol) = (v :: Symbol) | |
| MappingLeft '[] (v :: Symbol) = (() :: Type) | |
| MappingLeft '[] v = TypeError (Text "Cannot find value " :<>: ShowType v) | |
| MappingLeft ((x :-> y) ': rest) y = x | |
| MappingLeft (other ': rest) y = MappingLeft rest y |
Reflection to term-level
reflectSchema :: ReflectSchema s => Proxy s -> SchemaB TypeRep String String Source #
Reflect a schema into term-level.
reflectFields :: ReflectFields fs => Proxy fs -> [FieldDefB TypeRep String String] Source #
Reflect a list of fields into term-level.
reflectChoices :: ReflectChoices cs => Proxy cs -> [ChoiceDef String] Source #
Reflect a list of enumeration choices into term-level.
reflectFieldTypes :: ReflectFieldTypes ts => Proxy ts -> [FieldTypeB TypeRep String] Source #
Reflect a list of schema types into term-level.
reflectFieldType :: ReflectFieldType ty => Proxy ty -> FieldTypeB TypeRep String Source #
Reflect a schema type into term-level.
Supporting type classes
class KnownName (a :: k) where Source #
Type names and field names can be of any
kind, but for many uses we need a way
to turn them into strings at run-time.
This class generalizes KnownSymbol.
Instances
| KnownName False Source # | |
| KnownName True Source # | |
| KnownNat n => KnownName (n :: Nat) Source # | |
Defined in Mu.Schema.Definition | |
| KnownSymbol s => KnownName (s :: Symbol) Source # | |
Defined in Mu.Schema.Definition | |
| KnownName n => KnownName (ChoiceDef n :: ChoiceDef fieldName) Source # | |
| KnownName n => KnownName (FieldDef n t :: FieldDefB builtin typeName fieldName) Source # | |
| KnownName n => KnownName (DEnum n choices :: TypeDefB builtin typeName fieldName) Source # | |
| KnownName n => KnownName (DRecord n fields :: TypeDefB builtin typeName fieldName) Source # | |