\section{Stream Support} 

Three classes are provided by \cgal\ as adaptors to input and output stream
iterators.  The class \ccc{Istream_iterator} is an input iterator adaptor and 
is particularly useful for classes that are similar but not compatible to 
\ccc{std::istream}.  Similarly, the class \ccc{Ostream_iterator} is an output 
iterator adaptor.  The class \ccc{Verbose_ostream} can be used as an output 
stream. The stream
output operator \ccc{<<} is defined for any type. The class
stores in an internal state a stream and whether the
output is active or not. If the state is active, the stream output
operator \ccc{<<} uses the internal stream to output its argument. If
the state is inactive, nothing happens.