| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Language.Haskell.TH.Lift
Contents
Documentation
deriveLift' :: [Role] -> Info -> Q [Dec] Source #
Obtain Info values through a custom reification function. This is useful
when generating instances for datatypes that have not yet been declared.
makeLift :: Name -> Q Exp Source #
Generates a lambda expresson which behaves like lift (without requiring
a Lift instance). Example:
newtype Fix f = In { out :: f (Fix f) }
instance Lift (f (Fix f)) => Lift (Fix f) where
lift = $(makeLift ''Fix)
This can be useful when deriveLift is not clever enough to infer the
correct instance context, such as in the example above.
class Lift (t :: TYPE r) where #
A Lift instance can have any of its values turned into a Template
Haskell expression. This is needed when a value used within a Template
Haskell quotation is bound outside the Oxford brackets ([| ... |] or
[|| ... ||]) but not at the top level. As an example:
add1 :: Int -> Q (TExp Int) add1 x = [|| x + 1 ||]
Template Haskell has no way of knowing what value x will take on at
splice-time, so it requires the type of x to be an instance of Lift.
A Lift instance must satisfy $(lift x) ≡ x and $$(liftTyped x) ≡ x
for all x, where $(...) and $$(...) are Template Haskell splices.
It is additionally expected that lift x ≡ unTypeQ (liftTyped x)
Lift instances can be derived automatically by use of the -XDeriveLift
GHC language extension:
{-# LANGUAGE DeriveLift #-}
module Foo where
import Language.Haskell.TH.Syntax
data Bar a = Bar1 a (Bar a) | Bar2 String
deriving LiftRepresentation-polymorphic since template-haskell-2.16.0.0.
Minimal complete definition
Methods
lift :: Quote m => t -> m Exp #
Turn a value into a Template Haskell expression, suitable for use in a splice.
liftTyped :: forall (m :: Type -> Type). Quote m => t -> Code m t #
Turn a value into a Template Haskell typed expression, suitable for use in a typed splice.
Since: template-haskell-2.16.0.0
Instances
| Lift Addr# | Produces an Since: template-haskell-2.16.0.0 |
| Lift Double# | Since: template-haskell-2.16.0.0 |
| Lift Float# | Since: template-haskell-2.16.0.0 |
| Lift Int# | Since: template-haskell-2.16.0.0 |
| Lift ByteArray | Since: template-haskell-2.19.0.0 |
| Lift Void | Since: template-haskell-2.15.0.0 |
| Lift Int16 | |
| Lift Int32 | |
| Lift Int64 | |
| Lift Int8 | |
| Lift Word16 | |
| Lift Word32 | |
| Lift Word64 | |
| Lift Word8 | |
| Lift ModName Source # | |
| Lift Name Source # | |
| Lift NameFlavour Source # | |
Defined in Language.Haskell.TH.Lift Methods lift :: Quote m => NameFlavour -> m Exp # liftTyped :: forall (m :: Type -> Type). Quote m => NameFlavour -> Code m NameFlavour # | |
| Lift NameSpace Source # | |
| Lift OccName Source # | |
| Lift PkgName Source # | |
| Lift Integer | |
| Lift Natural | |
| Lift () | |
| Lift Bool | |
| Lift Char | |
| Lift Double | |
| Lift Float | |
| Lift Int | |
| Lift Word | |
| Lift Char# | Since: template-haskell-2.16.0.0 |
| Lift Word# | Since: template-haskell-2.16.0.0 |
| Lift (# #) | Since: template-haskell-2.16.0.0 |
| Lift a => Lift (NonEmpty a :: Type) | Since: template-haskell-2.15.0.0 |
| Integral a => Lift (Ratio a :: Type) | |
| Lift a => Lift (Maybe a :: Type) | |
| Lift a => Lift ([a] :: Type) | |
| (Lift a, Lift b) => Lift (Either a b :: Type) | |
| (Lift a, Lift b) => Lift ((a, b) :: Type) | |
| (Lift a, Lift b, Lift c) => Lift ((a, b, c) :: Type) | |
| (Lift a, Lift b, Lift c, Lift d) => Lift ((a, b, c, d) :: Type) | |
| (Lift a, Lift b, Lift c, Lift d, Lift e) => Lift ((a, b, c, d, e) :: Type) | |
| (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f) => Lift ((a, b, c, d, e, f) :: Type) | |
| (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f, Lift g) => Lift ((a, b, c, d, e, f, g) :: Type) | |
| Lift a => Lift ((# a #) :: TYPE ('TupleRep '[LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b) => Lift ((# a | b #) :: TYPE ('SumRep '[LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b) => Lift ((# a, b #) :: TYPE ('TupleRep '[LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c) => Lift ((# a | b | c #) :: TYPE ('SumRep '[LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c) => Lift ((# a, b, c #) :: TYPE ('TupleRep '[LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d) => Lift ((# a | b | c | d #) :: TYPE ('SumRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d) => Lift ((# a, b, c, d #) :: TYPE ('TupleRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d, Lift e) => Lift ((# a | b | c | d | e #) :: TYPE ('SumRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d, Lift e) => Lift ((# a, b, c, d, e #) :: TYPE ('TupleRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f) => Lift ((# a | b | c | d | e | f #) :: TYPE ('SumRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f) => Lift ((# a, b, c, d, e, f #) :: TYPE ('TupleRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f, Lift g) => Lift ((# a | b | c | d | e | f | g #) :: TYPE ('SumRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |
| (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f, Lift g) => Lift ((# a, b, c, d, e, f, g #) :: TYPE ('TupleRep '[LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep, LiftedRep])) | Since: template-haskell-2.16.0.0 |