[Write up local functions.
Bryan O'Sullivan <bos@serpentine.com>**20070919205327] {
hunk ./en/ch03-funcs-types.xml 869
+      <title>A few observations about complex numbers</title>
+
hunk ./en/ch03-funcs-types.xml 882
+
+    <sect2 id="hs.funcstypes.locals.functions">
+      <title>Local functions</title>
+
+      <para>You'll have noticed that Haskell's syntax for defining a
+	variable looks very similar to its syntax for defining a
+	function.  This symmetry is preserved in <code>let</code> and
+	<code>where</code> blocks; we can define local
+	<emphasis>functions</emphasis> just as easily as local
+	<emphasis>variables</emphasis>.  All of the same syntax
+	applies as at the top level: we can use multiple equations,
+	patterns, and guards.</para>
+
+      &LocalFunction.hs:pluralise;
+
+      <para>In this example, we define and use a local function
+	<function>plural</function> using several equations.  Local
+	functions can freely use variables from the scopes that
+	enclose them; here, we use <varname>word</varname> from the
+	definition of the outer function
+	<function>pluralise</function>.  In the definition of
+	<function>pluralise</function>, the <function>map</function>
+	function (which we'll be revisiting in the next chapter)
+	applies the local function <function>plural</function> to
+	every element of the <varname>counts</varname> list.</para>
+    </sect2>
addfile ./examples/ch03/LocalFunction.hs
hunk ./examples/ch03/LocalFunction.hs 1
+{-- snippet pluralise --}
+pluralise :: String -> [Int] -> [String]
+pluralise word counts = map plural counts
+    where plural 1 = "1 " ++ word
+          plural n = show n ++ " " ++ word ++ "s"
+{-- /snippet pluralise --}
}