Massive patch for the first months work adding System FC to GHC #21

[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..0ca2a53 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>
 
 
@@ -3871,8 +3903,8 @@ 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 +6062,7 @@ r)
                    GHCziBase.ZMZN GHCziBase.Char -> GHCziBase.ZMZN GHCziBase.Cha
 r) ->
               tpl2})
-        (%note "foo"
+        (%note "bar"
          eta);
 </programlisting>
 
@@ -6132,9 +6164,6 @@ 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.