[Forgot to document bail!
Bryan O'Sullivan <bos@serpentine.com>**20071216055517] {
hunk ./en/ch10-binary.xml 272
-      a similar purpose as our earlier
+      a similar purpose to our earlier
hunk ./en/ch10-binary.xml 296
-      of <type>Parse</type> values in a hidden argument.  Our
-      <function>parseByte</function> function doesn't take the parse
-      state as an argument.  Instead, it has to call
+      of <type>Parse</type> values in a hidden argument.</para>
+
+    <sect2>
+      <title>Obtaining and modifying the parse state</title>
+
+    <para>Our <function>parseByte</function> function doesn't take the
+      parse state as an argument.  Instead, it has to call
hunk ./en/ch10-binary.xml 337
+
+    </sect2>
+
+    <sect2>
+      <title>Reporting parse errors</title>
+
+      <para>We carefully defined our <type>Parse</type> type to
+	accommodate the possibility of failure.  The
+	<function>(==&gt;)</function> combinator checks for a parse
+	failure and stops parsing if it runs into a failure.  But we
+	haven't yet introduced the <function>bail</function> function,
+	which we use to report a parse error.</para>
+
+      &Parse.hs:bail;
+
+      <para>After we call <function>bail</function>,
+	<function>(==&gt;)</function> will successfully pattern match
+	on the <code>Left</code> constructor that it wraps the error
+	message with, and it will not invoke the next parser in the
+	chain.  This will cause the error message to percolate back
+	through the chain of prior callers.</para>
+    </sect2>
}