From 451415ebce0aec1bb51eeed7d7ae433184f19028 Mon Sep 17 00:00:00 2001
From: Joel de Guzman <djowel@gmail.com>
Date: Fri, 20 Mar 2009 01:21:42 +0000
Subject: [PATCH] fixed tuples::length not having a specialization for const
 tuple<> and const null_type

[SVN r51862]
---
 include/boost/tuple/detail/tuple_basic.hpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/boost/tuple/detail/tuple_basic.hpp b/include/boost/tuple/detail/tuple_basic.hpp
index ba59441..348fd80 100644
--- a/include/boost/tuple/detail/tuple_basic.hpp
+++ b/include/boost/tuple/detail/tuple_basic.hpp
@@ -213,7 +213,7 @@ struct element_impl<0, T, true /* IsConst */>
 
 
 template<int N, class T>
-struct element: 
+struct element:
   public detail::element_impl<N, T, ::boost::is_const<T>::value>
 {
 };
@@ -488,11 +488,20 @@ struct length<tuple<> > {
   BOOST_STATIC_CONSTANT(int, value = 0);
 };
 
+template<>
+struct length<tuple<> const> {
+  BOOST_STATIC_CONSTANT(int, value = 0);
+};
+
 template<>
 struct length<null_type> {
   BOOST_STATIC_CONSTANT(int, value = 0);
 };
 
+template<>
+struct length<null_type const> {
+  BOOST_STATIC_CONSTANT(int, value = 0);
+};
 
 namespace detail {