Added simple operators << and >> to optional<>

[SVN r32533]

include/boost/optional/optional_io.hpp

@@ -0,0 +1,64 @@
+// Copyright (C) 2005, Fernando Luis Cacciola Carballal.
+//
+// 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)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  fernando_cacciola@hotmail.com
+//
+#ifndef BOOST_OPTIONAL_OPTIONAL_IO_FLC_19NOV2002_HPP
+#define BOOST_OPTIONAL_OPTIONAL_IO_FLC_19NOV2002_HPP
+
+#include<ostream>
+#include<istream>
+
+
+#include "boost/optional/optional.hpp"
+#include "boost/utility/value_init.hpp"
+
+namespace boost
+{
+
+template<class CharType, class CharTrait, class T>
+inline
+std::basic_ostream<CharType, CharTrait>&
+operator<<(std::basic_ostream<CharType, CharTrait>& out, optional<T> const& v)
+{
+  if ( out.good() )
+  {
+    if ( !v )
+         out << "--" ;
+    else out << ' ' << *v ;
+  }
+
+  return out;
+}
+
+template<class CharType, class CharTrait, class T>
+inline
+std::basic_istream<CharType, CharTrait>&
+operator>>(std::basic_istream<CharType, CharTrait>& in, optional<T>& v)
+{
+  if ( in.good() )
+  {
+    int d = in.get();
+    if ( d == ' ' )
+    {
+      T x ;
+      in >> x;
+      v = x ;
+    }
+    else
+      v = optional<T>() ;
+  }
+
+  return in;
+}
+
+} // namespace boost
+
+#endif
+