-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | Create a unique hash value for a type.
--   
--   Produce a hash for a type that is unique for that type. The hash takes
--   both actual type names and type structure into account. This is useful
--   for checking the type of persisted values.
@package typehash
@version 1.2.0.0


-- | Produce a <i>hash</i> 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 expected value we can know if the
--   persistened value is of the correct type.
--   
--   The type code preserves the exact structure of the type and can be
--   used to check if one type is a subtype of another. If one type is a
--   subtype of another it means that, e.g., <tt>read . show</tt> will
--   correctly between the types. (Caveat <tt>read . show</tt> is only
--   guaranteed to work with named fields.)
--   
--   The type hash uses a cryptographic hash and can only be used to test
--   equality.
module Data.TypeHash

-- | Type codes.
data TypeCode

-- | Turn the type of the value into a type code.
typeCode :: (Data a) => a -> TypeCode

-- | Is the first type (code) as subtype of the second, i.e., can the first
--   type be converted to the second.
convertibleTo :: TypeCode -> TypeCode -> Bool

-- | Type hash.
data TypeHash

-- | Turn the type of the value into a type hash.
typeHash :: (Data a) => a -> TypeHash
instance Typeable Type
instance Typeable TypeHash
instance Typeable TypeCode
instance Eq Type
instance Ord Type
instance Show Type
instance Data Type
instance Eq TypeHash
instance Ord TypeHash
instance Data TypeHash
instance Show TypeHash
instance Read TypeHash
instance Eq TypeCode
instance Ord TypeCode
instance Data TypeCode
instance Show TypeCode