[Added -ftype-families to the user's manual
Manuel M T Chakravarty <chak@cse.unsw.edu.au>**20070515012036
 - This adds the option to the flag reference and puts a stub pointing to the
   Haskell wiki page about type families into the section about type extensions.
 - Once, the implementation has stabilised, the material from the wiki page 
   will be integreated into the user's manual.
] {
hunk ./docs/users_guide/flags.xml 695
+	    <row>
+	      <entry><option>-ftype-families</option></entry>
+	      <entry>Enable <link linkend="type-families">type families</link>.</entry>
+	      <entry>dynamic</entry>
+	      <entry><option>-fno-type-families</option></entry>
+	    </row>
hunk ./docs/users_guide/glasgow_exts.xml 4141
+
+<sect2 id="type-families">
+<title>Type families
+</title>
+
+<para>
+GHC supports the definition of type families indexed by types.  They may be
+seen as an extension of Haskell 98's class-based overloading of values to
+types.  When type families are declared in classes, they are also known as
+associated types.
+</para>
+<para>
+There are two forms of type families: data families and type synonym families.
+Currently, only the former are fully implemented, while we are still working
+on the latter.  As a result, the specification of the language extension is
+also still to some degree in flux.  Hence, a more detailed description of
+the language extension and its use is currently available
+from <ulink url="http://haskell.org/haskellwiki/GHC/Indexed_types">the Haskell
+wiki page on type families</ulink>.  The material will be moved to this user's
+guide when it has stabilised.
+</para>
+<para>
+Type families are enabled by the flag <option>-ftype-families</option>.
+</para>
+
+
+</sect2>
}