Data.TypeHash

Produce a hash for a type that is unique for that type. The hash takes both actual type names and type structure into account.

The purpose of the hash of a type is to be able to store the type of a persisted value together with the value. By comparing the type hash of a persisted value and the hash of expected type we can know if the persistened value is of the correct type.

The type hash uses a cryptographic hash and can only be used to test equality.

The type code preserves the exact structure of the type and can be used to check if one type is convertible to another in various ways.

This module uses the reflection offered by Typeable and Data to extract the information.

Documentation

data TypeCode

Type codes.

Instances

Eq TypeCode

Data TypeCode

Ord TypeCode

Show TypeCode

Typeable TypeCode

typeCode :: Data a => a -> TypeCode

Turn the type of the value into a type code.

convertibleIso :: TypeCode -> TypeCode -> Bool

Are the types strongly isomorphic, only allows change of type names.

convertibleWithReadShow :: TypeCode -> TypeCode -> Bool

Can read . show convert the first type to the second? Allows changing type names, allows permuting and/or adding constructors to the new type, also allows permuting named fields of a constructor.

convertibleWithJSON :: TypeCode -> TypeCode -> Bool

Can the generic JSON serializer and deserializer convert the first type to the second. Allows changing type names, allows permuting and/or adding constructors to the new type, also allows permuting and/or deleting named fields of a constructor. Furhermore, allows types with a single constructor to change constructor name.

data TypeHash

Type hash.

Instances

Eq TypeHash

Data TypeHash

Ord TypeHash

Read TypeHash

Show TypeHash

Typeable TypeHash

Binary TypeHash

typeHash :: Data a => a -> TypeHash

Turn the type of the value into a type hash.