Database.Record.Persistable

This module defines proposition interfaces for database value type and record type width.

Specify database value type

data PersistableSqlType q

Proposition to specify type q is database value type, contains null value

runPersistableNullValue :: PersistableSqlType q -> q

Null value of database value type q.

unsafePersistableSqlTypeFromNull

Arguments

:: q

null value of database value type q

-> PersistableSqlType q

Result proof object

Unsafely specify PersistableSqlType axiom from specified database null value which type is q.

Specify record width

type PersistableRecordWidth a = ProductConst (Sum Int) a

Proposition to specify width of Haskell type a. The width is length of database value list which is converted from Haskell type a.

runPersistableRecordWidth :: PersistableRecordWidth a -> Int

Get width Int value of record type a.

unsafePersistableRecordWidth

Arguments

:: Int

Specify width of Haskell type a

-> PersistableRecordWidth a

Result proof object

Unsafely specify PersistableRecordWidth axiom from specified width of Haskell type a.

unsafeValueWidth :: PersistableRecordWidth a

Unsafely specify PersistableRecordWidth axiom for Haskell type a which is single column type.

(<&>) :: PersistableRecordWidth a -> PersistableRecordWidth b -> PersistableRecordWidth (a, b)

Derivation rule of PersistableRecordWidth for tuple (,) type.

maybeWidth :: PersistableRecordWidth a -> PersistableRecordWidth (Maybe a)

Derivation rule of PersistableRecordWidth from from Haskell type a into for Haskell type Maybe a.

Implicit derivation rules, database value type and record type width

class Eq q => PersistableType q where

Interface of derivation rule for PersistableSqlType.

Minimal complete definition

persistableType

Methods

persistableType :: PersistableSqlType q

sqlNullValue :: PersistableType q => q

Implicitly derived null value of database value type.

class PersistableWidth a where

PersistableWidth a is implicit rule to derive PersistableRecordWidth a width proposition for type a.

Generic programming (https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#generic-programming) with default signature is available for PersistableWidth class, so you can make instance like below:

  {-# LANGUAGE DeriveGeneric #-}
  import GHC.Generics (Generic)
  --
  data Foo = Foo { ... } deriving Generic
  instance PersistableWidth Foo

Methods

persistableWidth :: PersistableRecordWidth a

persistableWidth :: (Generic a, GFieldWidthList (Rep a)) => PersistableRecordWidth a

Instances

PersistableWidth ()

Inference rule of PersistableRecordWidth for Haskell unit () type. Derive from axiom.

Methods

persistableWidth :: PersistableRecordWidth ()

PersistableWidth a => PersistableWidth (Maybe a)

Inference rule of PersistableRecordWidth proof object for Maybe type.

Methods

persistableWidth :: PersistableRecordWidth (Maybe a)

derivedWidth :: PersistableWidth a => (PersistableRecordWidth a, Int)

Pass type parameter and inferred width value.

low-level interfaces

class GFieldWidthList f

Generic width value list of record fields.

Minimal complete definition

gFieldWidthList

Instances

GFieldWidthList U1

Methods

gFieldWidthList :: ProductConst (DList Int) (U1 a)

PersistableWidth a => GFieldWidthList (K1 i a)

Methods

gFieldWidthList :: ProductConst (DList Int) (K1 i a a)

(GFieldWidthList a, GFieldWidthList b) => GFieldWidthList ((:*:) a b)

Methods

gFieldWidthList :: ProductConst (DList Int) ((a :*: b) a)

GFieldWidthList a => GFieldWidthList (M1 i c a)

Methods

gFieldWidthList :: ProductConst (DList Int) (M1 i c a a)

data ProductConst a b

Restricted in product isomorphism record type b

Instances

Show a => Show (ProductConst a b)

Methods

showsPrec :: Int -> ProductConst a b -> ShowS

show :: ProductConst a b -> String

showList :: [ProductConst a b] -> ShowS

getProductConst :: ProductConst a b -> a

extract constant value of ProductConst.

genericFieldOffsets :: (Generic a, GFieldWidthList (Rep a)) => ProductConst (Array Int Int) a

Generic offset array of record fields.