Doc typo

[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 8bca485..4475af4 100644 (file)
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -964,7 +964,7 @@ a data type with no constructors.  For example:</para>
 <para>Syntactically, the declaration lacks the "= constrs" part.  The 
 type can be parameterised over types of any kind, but if the kind is
 not <literal>*</literal> then an explicit kind annotation must be used
-(see <xref linkend="sec-kinding"/>).</para>
+(see <xref linkend="kinding"/>).</para>
 
 <para>Such data types have only one value, namely bottom.
 Nevertheless, they can be useful when defining "phantom types".</para>
@@ -1226,7 +1226,7 @@ that collection of packages in a uniform manner.  You can express
 quite a bit of object-oriented-like programming this way.
 </para>
 
-<sect4 id="existential">
+<sect3 id="existential">
 <title>Why existential?
 </title>
 
@@ -1249,9 +1249,9 @@ But Haskell programmers can safely think of the ordinary
 adding a new existential quantification construct.
 </para>
 
-</sect4>
+</sect3>
 
-<sect4>
+<sect3>
 <title>Type classes</title>
 
 <para>
@@ -1311,9 +1311,9 @@ Notice the way that the syntax fits smoothly with that used for
 universal quantification earlier.
 </para>
 
-</sect4>
+</sect3>
 
-<sect4 id="existential-records">
+<sect3 id="existential-records">
 <title>Record Constructors</title>
 
 <para>
@@ -1330,7 +1330,7 @@ data Counter a = forall self. NewCounter
 Here <literal>tag</literal> is a public field, with a well-typed selector
 function <literal>tag :: Counter a -> a</literal>.  The <literal>self</literal>
 type is hidden from the outside; any attempt to apply <literal>_this</literal>,
-<literal>_inc</literal> or <literal>_output</literal> as functions will raise a
+<literal>_inc</literal> or <literal>_display</literal> as functions will raise a
 compile-time error.  In other words, <emphasis>GHC defines a record selector function
 only for fields whose type does not mention the existentially-quantified variables</emphasis>.
 (This example used an underscore in the fields for which record selectors
@@ -1376,10 +1376,10 @@ setTag obj t = obj{ tag = t }
 
 </para>
 
-</sect4>
+</sect3>
 
 
-<sect4>
+<sect3>
 <title>Restrictions</title>
 
 <para>
@@ -1530,7 +1530,7 @@ declarations.  Define your own instances!
 
 </para>
 
-</sect4>
+</sect3>
 </sect2>
 
 <!-- ====================== Generalised algebraic data types =======================  -->
@@ -3372,7 +3372,7 @@ and you'd be right.  That is why they are an experimental feature.
 
 ================ END OF Linear Implicit Parameters commented out -->
 
-<sect2 id="sec-kinding">
+<sect2 id="kinding">
 <title>Explicitly-kinded quantification</title>
 
 <para>
@@ -3492,7 +3492,6 @@ including an operational type class context, is legal:
 <itemizedlist>
 <listitem> <para> On the left or right (see <literal>f4</literal>, for example)
 of a function arrow </para> </listitem>
-<listitem> <para> On the right of a function arrow (see <xref linkend="hoist"/>) </para> </listitem>
 <listitem> <para> As the argument of a constructor, or type of a field, in a data type declaration. For
 example, any of the <literal>f1,f2,f3,g1,g2</literal> above would be valid
 field type signatures.</para> </listitem>
@@ -4087,15 +4086,39 @@ The class <literal>IsString</literal> is defined as:
 class IsString a where
     fromString :: String -> a
 </programlisting>
-And the only predefined instance is the obvious one to make strings work as usual:
+The only predefined instance is the obvious one to make strings work as usual:
 <programlisting>
 instance IsString [Char] where
     fromString cs = cs
 </programlisting>
+The class <literal>IsString</literal> is not in scope by default.  If you want to mention
+it explicitly (for exmaple, to give an instance declaration for it), you can import it
+from module <literal>GHC.Exts</literal>.
+</para>
+<para>
+Haskell's defaulting mechanism is extended to cover string literals, when <option>-foverloaded-strings</option> is specified.
+Specifically:
+<itemizedlist>
+<listitem><para>
+Each type in a default declaration must be an 
+instance of <literal>Num</literal> <emphasis>or</emphasis> of <literal>IsString</literal>.
+</para></listitem>
+
+<listitem><para>
+The standard defaulting rule (<ulink url="http://haskell.org/onlinereport/decls.html#sect4.3.4">Haskell Report, Section 4.3.4</ulink>)
+is extended thus: defaulting applies when all the unresolved constraints involve standard classes
+<emphasis>or</emphasis> <literal>IsString</literal>; and at least one is a numeric class
+<emphasis>or</emphasis> <literal>IsString</literal>.
+</para></listitem>
+</itemizedlist>
 </para>
 <para>
 A small example:
 <programlisting>
+module Main where
+
+import GHC.Exts( IsString(..) )
+
 newtype MyString = MyString String deriving (Eq, Show)
 instance IsString MyString where
     fromString = MyString
@@ -4853,7 +4876,7 @@ Because the preprocessor targets Haskell (rather than Core),
 
 <!-- ==================== BANG PATTERNS =================  -->
 
-<sect1 id="sec-bang-patterns">
+<sect1 id="bang-patterns">
 <title>Bang patterns
 <indexterm><primary>Bang patterns</primary></indexterm>
 </title>
@@ -4868,7 +4891,7 @@ than the material below.
 Bang patterns are enabled by the flag <option>-fbang-patterns</option>.
 </para>
 
-<sect2 id="sec-bang-patterns-informal">
+<sect2 id="bang-patterns-informal">
 <title>Informal description of bang patterns
 </title>
 <para>
@@ -4923,7 +4946,7 @@ is part of the syntax of <literal>let</literal> bindings.
 </sect2>
 
 
-<sect2 id="sec-bang-patterns-sem">
+<sect2 id="bang-patterns-sem">
 <title>Syntax and semantics
 </title>
 <para>
@@ -4997,7 +5020,7 @@ a module.
 
 <!-- ==================== ASSERTIONS =================  -->
 
-<sect1 id="sec-assertions">
+<sect1 id="assertions">
 <title>Assertions
 <indexterm><primary>Assertions</primary></indexterm>
 </title>