Docs update

doc/Jamfile.v2

@@ -1,3 +1,13 @@
+# Tribool library
+
+# Copyright (C) 2002-2003 Douglas Gregor
+
+# Use, modification and distribution is subject to the Boost Software License,
+# Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+
+# For more information, see http://www.boost.org/
+
 project boost-sandbox/utility/doc ;
 import boostbook ;
 import doxygen ;

doc/tribool.boostbook

@@ -138,6 +138,18 @@ if (<functionname>indeterminate</functionname>(x)) {
 else {
   // report success or failure of x
 }</programlisting>
+
+  <para> All the logical operators and methods of <code><classname>tribool</classname></code> are marked
+  as <code>constexpr</code> in C++11. It means that <code><classname>tribool</classname></code> can
+  be used in compile time expressions:</para>
+
+  <programlisting>constexpr <classname>tribool</classname> x = (tribool(true) || tribool(indeterminate));
+<functionname>static_assert</functionname>(x, "Must be true!");
+</programlisting>
+
+  <note>Some compilers may have troubles with evaluating <code>tribool::operator safe_bool()</code> at compile time.</note>
+
+
 </section>
   
   <section>

test/tribool_test.cpp

@@ -130,6 +130,8 @@ int test_main(int, char*[])
   // Clang compiles well.
   //
   // constexpr bool res_safe_bool = tribool(true); // false
+  // constexpr tribool xxx = (tribool(true) || tribool(indeterminate));
+  // static_assert(xxx, "Must be true!");
 #endif
 
   std::cout << "no errors detected\n";