Three improvements to Template Haskell (fixes #3467)

[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 bf2e9ac..fb21918 100644 (file)
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -6065,12 +6065,11 @@ Wiki page</ulink>.
                    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>
+                   <listitem><para> a list of top-level declarations; the spliced expression 
+                    must have type <literal>Q [Dec]</literal></para></listitem>
                    </itemizedlist>
-               </para>
            Inside a splice you can can only call functions defined in imported modules,
-       not functions defined elsewhere in the same module.</listitem>
-
+       not functions defined elsewhere in the same module.</para></listitem>
 
              <listitem><para>
                  A expression quotation is written in Oxford brackets, thus:
@@ -6087,7 +6086,7 @@ Wiki page</ulink>.
                  A quasi-quotation can appear in either a pattern context or an
                  expression context and is also written in Oxford brackets:
                  <itemizedlist>
-                   <listitem><para> <literal>[:<replaceable>varid</replaceable>| ... |]</literal>,
+                   <listitem><para> <literal>[$<replaceable>varid</replaceable>| ... |]</literal>,
                         where the "..." is an arbitrary string; a full description of the
                        quasi-quotation facility is given in <xref linkend="th-quasiquotation"/>.</para></listitem>
                  </itemizedlist></para></listitem>
@@ -6108,6 +6107,25 @@ Wiki page</ulink>.
                 </para>
                </listitem>
 
+             <listitem><para> You may omit the <literal>$(...)</literal> in a top-level declaration splice. 
+              Simply writing an expression (rather than a declaration) implies a splice.  For example, you can write
+<programlisting>
+module Foo where
+import Bar
+
+f x = x
+
+$(deriveStuff 'f)   -- Uses the $(...) notation
+
+g y = y+1
+
+deriveStuff 'g      -- Omits the $(...)
+
+h z = z-1
+</programlisting>
+            This abbreviation makes top-level declaration slices quieter and less intimidating.
+           </para></listitem>
+
                  
        </itemizedlist>
 (Compared to the original paper, there are many differences of detail.