diff options
Diffstat (limited to 'docs')
-rw-r--r-- | docs/users_guide/8.10.1-notes.rst | 6 | ||||
-rw-r--r-- | docs/users_guide/glasgow_exts.rst | 32 |
2 files changed, 18 insertions, 20 deletions
diff --git a/docs/users_guide/8.10.1-notes.rst b/docs/users_guide/8.10.1-notes.rst index 21a7f2b275..1c47a002d7 100644 --- a/docs/users_guide/8.10.1-notes.rst +++ b/docs/users_guide/8.10.1-notes.rst @@ -73,6 +73,12 @@ Runtime system Template Haskell ~~~~~~~~~~~~~~~~ +- The ``Lift`` typeclass is now levity-polymorphic and has a ``liftTyped`` + method. Previously disallowed instances for unboxed tuples, unboxed sums, an + primitive unboxed types have also been added. Finally, the code generated by + :ghc-flags:`-XDeriveLift` has been simplified to take advantage of expression + quotations. + ``ghc-prim`` library ~~~~~~~~~~~~~~~~~~~~ diff --git a/docs/users_guide/glasgow_exts.rst b/docs/users_guide/glasgow_exts.rst index 1c1d4cbb85..781a10691e 100644 --- a/docs/users_guide/glasgow_exts.rst +++ b/docs/users_guide/glasgow_exts.rst @@ -4531,7 +4531,8 @@ Deriving ``Lift`` instances The class ``Lift``, unlike other derivable classes, lives in ``template-haskell`` instead of ``base``. Having a data type be an instance of ``Lift`` permits its values to be promoted to Template Haskell expressions (of -type ``ExpQ``), which can then be spliced into Haskell source code. +type ``ExpQ`` and ``TExpQ a``), which can then be spliced into Haskell source +code. Here is an example of how one can derive ``Lift``: @@ -4546,17 +4547,11 @@ Here is an example of how one can derive ``Lift``: {- instance (Lift a) => Lift (Foo a) where - lift (Foo a) - = appE - (conE - (mkNameG_d "package-name" "Bar" "Foo")) - (lift a) - lift (u :^: v) - = infixApp - (lift u) - (conE - (mkNameG_d "package-name" "Bar" ":^:")) - (lift v) + lift (Foo a) = [| Foo a |] + lift ((:^:) u v) = [| (:^:) u v |] + + liftTyped (Foo a) = [|| Foo a ||] + liftTyped ((:^:) u v) = [|| (:^:) u v ||] -} ----- @@ -4572,8 +4567,9 @@ Here is an example of how one can derive ``Lift``: fooExp :: Lift a => Foo a -> Q Exp fooExp f = [| f |] -:extension:`DeriveLift` also works for certain unboxed types (``Addr#``, ``Char#``, -``Double#``, ``Float#``, ``Int#``, and ``Word#``): +Note that the ``Lift`` typeclass takes advantage of :ref:`runtime-rep` in order +to support instances involving unboxed types. This means :extension:`DeriveLift` +also works for these types: :: @@ -4587,12 +4583,8 @@ Here is an example of how one can derive ``Lift``: {- instance Lift IntHash where - lift (IntHash i) - = appE - (conE - (mkNameG_d "package-name" "Unboxed" "IntHash")) - (litE - (intPrimL (toInteger (I# i)))) + lift (IntHash i) = [| IntHash i |] + liftTyped (IntHash i) = [|| IntHash i ||] -} |