Mention that generalised list comprehensions are enabled with -XTransformListComp

[ghc-hetmet.git] / docs / users_guide / glasgow_exts.xml

diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml
index f63c90e..a08ace9 100644 (file)
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -1008,6 +1008,7 @@ This name is not supported by GHC.
        paper <ulink url="http://research.microsoft.com/~simonpj/papers/list-comp">
          Comprehensive comprehensions: comprehensions with "order by" and "group by"</ulink>,
     except that the syntax we use differs slightly from the paper.</para>
+<para>The extension is enabled with the flag <option>-XTransformListComp</option>.</para>
 <para>Here is an example: 
 <programlisting>
 employees = [ ("Simon", "MS", 80)
@@ -2353,6 +2354,16 @@ otherwise is a <emphasis>generalised</emphasis> data type (<xref linkend="gadt"/
 </para></listitem>
 
 <listitem><para>
+As with other type signatures, you can give a single signature for several data constructors.
+In this example we give a single signature for <literal>T1</literal> and <literal>T2</literal>:
+<programlisting>
+  data T a where
+    T1,T2 :: a -> T a
+    T3 :: T a
+</programlisting>
+</para></listitem>
+
+<listitem><para>
 The type signature of
 each constructor is independent, and is implicitly universally quantified as usual. 
 Different constructors may have different universally-quantified type variables
@@ -2682,7 +2693,7 @@ GHC always treats the <emphasis>last</emphasis> parameter of the instance
 
 
 <sect2 id="deriving-typeable">
-<title>Deriving clause for classes <literal>Typeable</literal> and <literal>Data</literal></title>
+<title>Deriving clause for extra classes (<literal>Typeable</literal>, <literal>Data</literal>, etc)</title>
 
 <para>
 Haskell 98 allows the programmer to add "<literal>deriving( Eq, Ord )</literal>" to a data type 
@@ -2692,11 +2703,11 @@ classes <literal>Eq</literal>, <literal>Ord</literal>,
 <literal>Enum</literal>, <literal>Ix</literal>, <literal>Bounded</literal>, <literal>Read</literal>, and <literal>Show</literal>.
 </para>
 <para>
-GHC extends this list with two more classes that may be automatically derived 
-(provided the <option>-XDeriveDataTypeable</option> flag is specified):
-<literal>Typeable</literal>, and <literal>Data</literal>.  These classes are defined in the library
-modules <literal>Data.Typeable</literal> and <literal>Data.Generics</literal> respectively, and the
-appropriate class must be in scope before it can be mentioned in the <literal>deriving</literal> clause.
+GHC extends this list with several more classes that may be automatically derived:
+<itemizedlist>
+<listitem><para> With <option>-XDeriveDataTypeable</option>, you can derive instances of the classes
+<literal>Typeable</literal>, and <literal>Data</literal>, defined in the library
+modules <literal>Data.Typeable</literal> and <literal>Data.Generics</literal> respectively.
 </para>
 <para>An instance of <literal>Typeable</literal> can only be derived if the
 data type has seven or fewer type parameters, all of kind <literal>*</literal>.
@@ -2712,6 +2723,26 @@ In other cases, there is nothing to stop the programmer writing a <literal>Typab
 class, whose kind suits that of the data type constructor, and
 then writing the data type instance by hand.
 </para>
+</listitem>
+
+<listitem><para> With <option>-XDeriveFunctor</option>, you can derive instances of 
+the class <literal>Functor</literal>,
+defined in <literal>GHC.Base</literal>.
+</para></listitem>
+
+<listitem><para> With <option>-XDeriveFoldable</option>, you can derive instances of 
+the class <literal>Foldable</literal>,
+defined in <literal>Data.Foldable</literal>.
+</para></listitem>
+
+<listitem><para> With <option>-XDeriveTraversable</option>, you can derive instances of 
+the class <literal>Traversable</literal>,
+defined in <literal>Data.Traversable</literal>.
+</para></listitem>
+</itemizedlist>
+In each case the appropriate class must be in scope before it 
+can be mentioned in the <literal>deriving</literal> clause.
+</para>
 </sect2>
 
 <sect2 id="newtype-deriving">
@@ -5833,6 +5864,8 @@ Wiki page</ulink>.
                  <itemizedlist>
                    <listitem><para> an expression; the spliced expression must
                    have type <literal>Q Exp</literal></para></listitem>
+                   <listitem><para> an type; the spliced expression must
+                   have type <literal>Q Typ</literal></para></listitem>
                    <listitem><para> a list of top-level declarations; the spliced expression must have type <literal>Q [Dec]</literal></para></listitem>
                    </itemizedlist>
                </para>
@@ -5881,7 +5914,7 @@ Wiki page</ulink>.
 (Compared to the original paper, there are many differences of detail.
 The syntax for a declaration splice uses "<literal>$</literal>" not "<literal>splice</literal>".
 The type of the enclosed expression must be  <literal>Q [Dec]</literal>, not  <literal>[Q Dec]</literal>.
-Type splices are not implemented, and neither are pattern splices or quotations.
+Pattern splices and quotations are not implemented.)
 
 </sect2>