X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=docs%2Fusers_guide%2Fglasgow_exts.xml;h=052c9c3dea317662a2e163aa8a1dc30bef852cca;hp=f8ad5c1b0ac8a79f9ee96c6a4227e6abafcaa6e7;hb=b55fe864599e77f2ae2a3fbeec899ea7aeeac9f2;hpb=9da4639011348fb6c318e3cba4b08622f811d9c4 diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml index f8ad5c1..052c9c3 100644 --- a/docs/users_guide/glasgow_exts.xml +++ b/docs/users_guide/glasgow_exts.xml @@ -106,9 +106,7 @@ documentation describes all the libraries that come with GHC. This option enables the language extension defined in the - Haskell 98 Foreign Function Interface Addendum plus deprecated - syntax of previous versions of the FFI for backwards - compatibility. + Haskell 98 Foreign Function Interface Addendum. New reserved words: foreign. @@ -116,7 +114,7 @@ documentation describes all the libraries that come with GHC. - ,: + ,: These two flags control how generalisation is done. @@ -3727,6 +3725,33 @@ the standard method is used or the one described here.) + +Stand-alone deriving declarations + + +GHC now allows stand-alone deriving declarations: + + + + data Foo = Bar Int | Baz String + + deriving Eq for Foo + + +Deriving instances of multi-parameter type classes for newtypes is +also allowed: + + + newtype Foo a = MkFoo (State Int a) + + deriving (MonadState Int) for Foo + + + + + + + Generalised typing of mutually recursive bindings @@ -6105,6 +6130,22 @@ r) -> described in this section. All are exported by GHC.Exts. + The <literal>seq</literal> function + +The function seq is as described in the Haskell98 Report. + + seq :: a -> b -> b + +It evaluates its first argument to head normal form, and then returns its +second argument as the result. The reason that it is documented here is +that, despite seq's polymorphism, its +second argument can have an unboxed type, or +can be an unboxed tuple; for example (seq x 4#) +or (seq x (# p,q #)). This requires b +to be instantiated to an unboxed type, which is not usually allowed. + + + The <literal>inline</literal> function The inline function is somewhat experimental. @@ -6163,6 +6204,11 @@ If lazy were not lazy, par would look strict in y which would defeat the whole purpose of par. + +Like seq, the argument of lazy can have +an unboxed type. + + The <literal>unsafeCoerce#</literal> function @@ -6178,7 +6224,14 @@ It is generally used when you want to write a program that you know is well-typed, but where Haskell's type system is not expressive enough to prove that it is well typed. + +The argument to unsafeCoerce# can have unboxed types, +although extremely bad things will happen if you coerce a boxed type +to an unboxed type. + + +