From c506d2537fda683486c882262210e7c87deaf7a2 Mon Sep 17 00:00:00 2001
From: Neil Groves <neil@grovescomputing.com>
Date: Sun, 26 Dec 2010 23:14:08 +0000
Subject: [PATCH] [boost][range] - Trac item 4226 - Implemented a safe_bool
 utility class that is intended to be refactored into a core area. Integrated
 this into iterator_range.

[SVN r67463]
---
 include/boost/range/adaptor/strided.hpp     |  4 --
 include/boost/range/detail/safe_bool.hpp    | 72 +++++++++++++++++++++
 include/boost/range/iterator_range_core.hpp | 20 +++---
 3 files changed, 81 insertions(+), 15 deletions(-)
 create mode 100644 include/boost/range/detail/safe_bool.hpp

diff --git a/include/boost/range/adaptor/strided.hpp b/include/boost/range/adaptor/strided.hpp
index a391eef..abfad5e 100755
--- a/include/boost/range/adaptor/strided.hpp
+++ b/include/boost/range/adaptor/strided.hpp
@@ -15,7 +15,6 @@
 #include <boost/range/iterator_range.hpp>
 #include <boost/iterator/iterator_adaptor.hpp>
 #include <iterator>
-#include <iostream>
 
 namespace boost
 {
@@ -206,14 +205,11 @@ namespace boost
         private:
             void increment()
             {
-                std::cout << "increment() - before = " << (this->base_reference() - m_first);
                 base_iterator& it = this->base_reference();
                 if ((m_last - it) > m_stride)
                     it += m_stride;
                 else
                     it = m_last;
-
-                std::cout << " after = " << (this->base_reference() - m_first) << std::endl;
             }
 
             void decrement()
diff --git a/include/boost/range/detail/safe_bool.hpp b/include/boost/range/detail/safe_bool.hpp
new file mode 100644
index 0000000..182e510
--- /dev/null
+++ b/include/boost/range/detail/safe_bool.hpp
@@ -0,0 +1,72 @@
+//  This header intentionally has no include guards.
+//
+//  Copyright (c) 2010 Neil Groves
+//  Distributed under 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
+//
+// This code utilises the experience gained during the evolution of
+// <boost/smart_ptr/operator_bool.hpp>
+#ifndef BOOST_RANGE_SAFE_BOOL_INCLUDED_HPP
+#define BOOST_RANGE_SAFE_BOOL_INCLUDED_HPP
+
+#include <boost/config.hpp>
+#include <boost/range/config.hpp>
+
+namespace boost
+{
+    namespace range_detail
+    {
+
+template<class DataMemberPtr>
+class safe_bool
+{
+public:
+    typedef safe_bool this_type;
+
+#if (defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, < 0x570)) || defined(__CINT_)
+    typedef bool unspecified_bool_type;
+    static unspecified_bool_type to_unspecified_bool(const bool x, DataMemberPtr)
+    {
+        return x;
+    }
+#elif defined(_MANAGED)
+    static void unspecified_bool(this_type***)
+    {
+    }
+    typedef void(*unspecified_bool_type)(this_type***);
+    static unspecified_bool_type to_unspecified_bool(const bool x, DataMemberPtr)
+    {
+        return x ? unspecified_bool : 0;
+    }
+#elif \
+    ( defined(__MWERKS__) && BOOST_WORKAROUND(__MWERKS__, < 0x3200) ) || \
+    ( defined(__GNUC__) && (__GNUC__ * 100 + __GNUC_MINOR__ < 304) ) || \
+    ( defined(__SUNPRO_CC) && BOOST_WORKAROUND(__SUNPRO_CC, <= 0x590) )
+
+    typedef bool (this_type::*unspecified_bool_type)() const;
+
+    static unspecified_bool_type to_unspecified_bool(const bool x, DataMemberPtr)
+    {
+        return x ? &this_type::detail_safe_bool_member_fn : 0;
+    }
+private:
+    bool detail_safe_bool_member_fn() const { return false; }
+#else
+    typedef DataMemberPtr unspecified_bool_type;
+    static unspecified_bool_type to_unspecified_bool(const bool x, DataMemberPtr p)
+    {
+        return x ? p : 0;
+    }
+#endif
+private:
+    safe_bool();
+    safe_bool(const safe_bool&);
+    void operator=(const safe_bool&);
+    ~safe_bool();
+};
+
+    } // namespace range_detail
+} // namespace boost
+
+#endif // include guard
diff --git a/include/boost/range/iterator_range_core.hpp b/include/boost/range/iterator_range_core.hpp
index ab1e80e..7664c2e 100755
--- a/include/boost/range/iterator_range_core.hpp
+++ b/include/boost/range/iterator_range_core.hpp
@@ -27,6 +27,7 @@
 #include <boost/range/iterator.hpp>
 #include <boost/range/difference_type.hpp>
 #include <boost/range/algorithm/equal.hpp>
+#include <boost/range/detail/safe_bool.hpp>
 #include <boost/utility/enable_if.hpp>
 #include <iterator>
 #include <algorithm>
@@ -81,7 +82,6 @@ namespace boost
 
         struct range_tag { };
         struct const_range_tag { };
-
     }
 
 //  iterator range template class -----------------------------------------//
@@ -106,13 +106,14 @@ namespace boost
         template<class IteratorT>
         class iterator_range
         {
+            typedef range_detail::safe_bool< IteratorT iterator_range<IteratorT>::* > safe_bool_t;
         protected: // Used by sub_range
             //! implementation class
             typedef iterator_range_detail::iterator_range_impl<IteratorT> impl;
         public:
-
             //! this type
             typedef iterator_range<IteratorT> type;
+            typedef BOOST_DEDUCED_TYPENAME safe_bool_t::unspecified_bool_type unspecified_bool_type;
             //BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION(value_type);
 
             //! Encapsulated value type
@@ -238,18 +239,15 @@ namespace boost
                 return m_Begin == m_End;
             }
 
-#if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
-            operator bool() const
-            {
-                return !empty();
-            }
-#else
-            typedef iterator (iterator_range::*unspecified_bool_type) () const;
             operator unspecified_bool_type() const
             {
-                return empty() ? 0: &iterator_range::end;
+                return safe_bool_t::to_unspecified_bool(m_Begin != m_End, &iterator_range::m_Begin);
+            }
+
+            bool operator!() const
+            {
+                return empty();
             }
-#endif
 
             bool equal( const iterator_range& r ) const
             {