Database.HaskRel.Relational.Variable

Relation variable definition, along with IO level support functions.

Relation variable definitions

data Relvar a

Relation variable reference. This type has a phantom type variable, which generally calls for the type to be explicity specified:

 s = Relvar "SuppliersPartsDB/S.rv" :: Relvar '[SNO, SName, Status, City]

Constructors

Relvar

Fields

relvarPath :: FilePath

Instances

Typeable [*] a => Show (Relvar a)

(Ord (HList b), Read (HList (RecordValuesR b)), Typeable [*] b, RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b, HFoldr (Mapcar HPresentTypedRecAttr) [[String]] (RecordValuesR b) [[String]], HFoldr (Mapcar HPresentRecAttr) [[String]] (RecordValuesR b) [[String]]) => HFWPresent (Relvar b)

(Ord (HList b), Read (HList (RecordValuesR b)), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => RelAssign (Relvar b)

(Ord (HList b), Read (HList (RecordValuesR b)), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => MonOp (Relvar b)

(Ord (HList b), Read (HList (RecordValuesR b)), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => DyaOp (IO (Relation a)) (Relvar b)

(Ord (HList b), Read (HList (RecordValuesR b)), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => DyaOp (Relation a) (Relvar b)

(Ord (HList a), Ord (HList b), Read (HList (RecordValuesR a)), Read (HList (RecordValuesR b)), RecordValues a, RecordValues b, HMapAux HList TaggedFn (RecordValuesR a) a, HMapAux HList TaggedFn (RecordValuesR b) b) => DyaOp (Relvar a) (Relvar b)

(Ord (HList a), Read (HList (RecordValuesR a)), RecordValues a, HMapAux HList TaggedFn (RecordValuesR a) a) => DyaOp (Relvar a) (IO (Relation b))

(Ord (HList a), Read (HList (RecordValuesR a)), RecordValues a, HMapAux HList TaggedFn (RecordValuesR a) a) => DyaOp (Relvar a) (Relation b)

type RelAssignArg (Relvar b) = Relation b

type DyaOpLeft (Relvar a) = Relation a

type DyaOpLeft (Relvar a) = Relation a

type DyaOpLeft (Relvar a) = Relation a

type DyaOpRight (Relvar b) = Relation b

type DyaOpRight (Relvar b) = Relation b

type DyaOpRight (Relvar b) = Relation b

type MonOpArg (Relvar b) = Relation b

type MonOpRes (Relvar b) res = IO res

type DyaOpRes (IO (Relation a)) (Relvar b) res = IO res

type DyaOpRes (Relation a) (Relvar b) res = IO res

type DyaOpRes (Relvar a) (Relvar b) res = IO res

type DyaOpRes (Relvar a) (IO (Relation b)) res = IO res

type DyaOpRes (Relvar a) (Relation b) res = IO res

relvarType :: Relvar a -> Relation a

Gives the type a relvar results in. Note that the value this results in will always be undefined.

Relational input

readRel :: forall b. (Ord (HList b), Read (HList (RecordValuesR b)), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => String -> Relation b

Reads a relation value from a string containing HLists of unpacked attribues.

>>> pt$ ( readRel "H[\"S1\",10],H[\"S2\",50]" :: Relation '[SNO,Status])
┌───────────────┬───────────────────┐
│ sno :: String │ status :: Integer │
╞═══════════════╪═══════════════════╡
│ S1            │ 10                │
│ S2            │ 50                │
└───────────────┴───────────────────┘

readRelvar :: (Ord (HList b), Read (HList (RecordValuesR b)), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => Relvar b -> IO (Relation b)

Read a relation variable from the file referenced by the first argument

hListsToRel :: (Ord (HList b), RecordValues b, HMapAux HList TaggedFn (RecordValuesR b) b) => [HList (RecordValuesR b)] -> Relation b

Converts a list of HLists into a relation value.

Relational output

writeRelvarBody :: Show r => FilePath -> r -> IO ()

Writes a body of a relvar to a given file

writeRelvarBody' :: Show r => Relvar rv -> r -> IO ()

Writes a body of a relvar to a given relvar file reference

showRelStr :: (Show (HList (RecordValuesR r)), RecordValues r) => Relation r -> String

Prints a relation as a list without the outer brackets.