*** empty log message ***

[SVN r24637]

include/boost/range/iterator_range.hpp

@@ -75,34 +75,54 @@ namespace boost {
             //! iterator type
             typedef IteratorT iterator;
 
+            iterator_range() : m_Begin( iterator() ), m_End( iterator() ), 
+                               singular( true )
+            { }
+            
             //! Constructor from a pair of iterators
             template< class Iterator >
             iterator_range( Iterator Begin, Iterator End ) : 
-                m_Begin(Begin), m_End(End) {}
+                m_Begin(Begin), m_End(End), singular(false) {}
 
             //! Constructor from a Range
             template< class Range >
             iterator_range( const Range& r ) : 
-                m_Begin( boost::begin( r ) ), m_End( boost::end( r ) ) {}
+                m_Begin( boost::begin( r ) ), m_End( boost::end( r ) ), 
+                singular(false) {}
 
             //! Constructor from a Range
             template< class Range >
             iterator_range( Range& r ) : 
-            m_Begin( boost::begin( r ) ), m_End( boost::end( r ) ) {}
+                m_Begin( boost::begin( r ) ), m_End( boost::end( r ) ), 
+                singular(false) {}
+            
+            template< class Iterator >
+            iterator_range& operator=( const iterator_range<Iterator>& r )    
+            {
+                m_Begin  = r.begin(); 
+                m_End    = r.end();
+                //
+                // remark: this need not necessarily be true, but it does no harm
+                //
+                singular = r.empty();
+                return *this;
+            }
                                       
             template< class ForwardRange >
             iterator_range& operator=( ForwardRange& r )
             {
-                m_Begin = boost::begin( r ); 
-                m_End   = boost::end( r );
+                m_Begin  = boost::begin( r ); 
+                m_End    = boost::end( r );
+                singular = false;
                 return *this;
             }
 
             template< class ForwardRange >
             iterator_range& operator=( const ForwardRange& r )
             {
-                m_Begin = boost::begin( r ); 
-                m_End   = boost::end( r );
+                m_Begin  = boost::begin( r ); 
+                m_End    = boost::end( r );
+                singular = false;
                 return *this;
             }
 
@@ -130,11 +150,17 @@ namespace boost {
             */
             size_type size() const
             { 
+                if( singular )
+                    return 0;
+                
                 return std::distance( m_Begin, m_End );
             }
             
             bool empty() const
             {
+                if( singular )
+                    return true;
+                
                 return m_Begin == m_End;
             }
 
@@ -160,7 +186,7 @@ namespace boost {
             // begin and end iterators
             IteratorT m_Begin;
             IteratorT m_End;
-            
+            bool      singular;
         };
 
 //  iterator range free-standing operators ---------------------------//

include/boost/range/sub_range.hpp

@@ -35,6 +35,9 @@ namespace boost
         typedef BOOST_DEDUCED_TYPENAME range_size<ForwardRange>::type             size_type;
 
     public:
+        sub_range() : base() 
+        { }
+            
         template< class ForwardRange2 >
         sub_range( ForwardRange2& r ) : base( r )
         { }
@@ -68,7 +71,7 @@ namespace boost
         const_iterator  begin() const    { return base::begin(); }
         iterator        end()            { return base::end();   }
         const_iterator  end() const      { return base::end();   }
-        size_type       size() const     { return std::distance( begin(), end() ); }   
+        size_type       size() const     { return base::size();  }   
 
     };
         

test/sub_range.cpp

@@ -113,6 +113,14 @@ void check_iterator_range()
     r.size();
     s.size();
     
+    irange singular_irange;
+    BOOST_CHECK( singular_irange.empty() );
+    BOOST_CHECK( singular_irange.size() == 0 );
+    
+    srange singular_srange;
+    BOOST_CHECK( singular_srange.empty() );
+    BOOST_CHECK( singular_srange.size() == 0 );
+
 }