Move snocView in the file, nearer the other spliting functions

[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 d60e8e9..afb4447 100644 (file)
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -905,6 +905,38 @@ fromInteger :: Integer -> Bool -> Bool
             you should be all right.</para>
 
 </sect2>
+
+<sect2 id="postfix-operators">
+<title>Postfix operators</title>
+
+<para>
+GHC allows a small extension to the syntax of left operator sections, which
+allows you to define postfix operators.  The extension is this:  the left section
+<programlisting>
+  (e !)
+</programlisting> 
+is equivalent (from the point of view of both type checking and execution) to the expression
+<programlisting>
+  ((!) e)
+</programlisting> 
+(for any expression <literal>e</literal> and operator <literal>(!)</literal>.
+The strict Haskell 98 interpretation is that the section is equivalent to
+<programlisting>
+  (\y -> (!) e y)
+</programlisting> 
+That is, the operator must be a function of two arguments.  GHC allows it to
+take only one argument, and that in turn allows you to write the function
+postfix.
+</para>
+<para>Since this extension goes beyond Haskell 98, it should really be enabled
+by a flag; but in fact it is enabled all the time.  (No Haskell 98 programs
+change their behaviour, of course.)
+</para>
+<para>The extension does not extend to the left-hand side of function
+definitions; you must define such a function in prefix form.</para>
+
+</sect2>
+
 </sect1>
 
 
@@ -3608,16 +3640,19 @@ declaration (after expansion of any type synonyms)
 where 
  <itemizedlist>
 <listitem><para>
-  The type <literal>t</literal> is an arbitrary type
+  The <literal>ci</literal> are partial applications of
+  classes of the form <literal>C t1'...tj'</literal>, where the arity of <literal>C</literal>
+  is exactly <literal>j+1</literal>.  That is, <literal>C</literal> lacks exactly one type argument.
 </para></listitem>
 <listitem><para>
-  The <literal>vk+1...vn</literal> are type variables which do not occur in 
-  <literal>t</literal>, and
+  The <literal>k</literal> is chosen so that <literal>ci (T v1...vk)</literal> is well-kinded.
 </para></listitem>
 <listitem><para>
-  The <literal>ci</literal> are partial applications of
-  classes of the form <literal>C t1'...tj'</literal>, where the arity of <literal>C</literal>
-  is exactly <literal>j+1</literal>.  That is, <literal>C</literal> lacks exactly one type argument.
+  The type <literal>t</literal> is an arbitrary type.
+</para></listitem>
+<listitem><para>
+  The type variables <literal>vk+1...vn</literal> do not occur in <literal>t</literal>, 
+  nor in the <literal>ci</literal>, and
 </para></listitem>
 <listitem><para>
   None of the <literal>ci</literal> is <literal>Read</literal>, <literal>Show</literal>, 
@@ -3630,13 +3665,8 @@ where
 Then, for each <literal>ci</literal>, the derived instance
 declaration is:
 <programlisting> 
-  instance ci (t vk+1...v) => ci (T v1...vp)
+  instance ci t => ci (T v1...vk)
 </programlisting>
-where <literal>p</literal> is chosen so that <literal>T v1...vp</literal> is of the 
-right <emphasis>kind</emphasis> for the last parameter of class <literal>Ci</literal>.
-</para>
-<para>
-
 As an example which does <emphasis>not</emphasis> work, consider 
 <programlisting> 
   newtype NonMonad m s = NonMonad (State s m s) deriving Monad 
@@ -3871,8 +3901,8 @@ declaration, but only if the data type could also have been declared in
 Haskell-98 syntax.   For example, these two declarations are equivalent
 <programlisting>
   data Maybe1 a where {
-      Nothing1 :: Maybe a ;
-      Just1    :: a -> Maybe a
+      Nothing1 :: Maybe1 a ;
+      Just1    :: a -> Maybe1 a
     } deriving( Eq, Ord )
 
   data Maybe2 a = Nothing2 | Just2 a 
@@ -6030,7 +6060,7 @@ r)
                    GHCziBase.ZMZN GHCziBase.Char -> GHCziBase.ZMZN GHCziBase.Cha
 r) ->
               tpl2})
-        (%note "foo"
+        (%note "bar"
          eta);
 </programlisting>
 
@@ -6132,9 +6162,6 @@ that it is well typed.
 <sect1 id="generic-classes">
 <title>Generic classes</title>
 
-    <para>(Note: support for generic classes is currently broken in
-    GHC 5.02).</para>
-
 <para>
 The ideas behind this extension are described in detail in "Derivable type classes",
 Ralf Hinze and Simon Peyton Jones, Haskell Workshop, Montreal Sept 2000, pp94-105.