整理

include/boost/iterator/is_readable_iterator.hpp

@@ -0,0 +1,69 @@
+// Copyright David Abrahams 2003. 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)
+#ifndef IS_READABLE_ITERATOR_DWA2003112_HPP
+#define IS_READABLE_ITERATOR_DWA2003112_HPP
+
+#include <iterator>
+#include <type_traits>
+
+namespace boost {
+namespace iterators {
+namespace detail {
+
+// Guts of is_readable_iterator.  It is the iterator type and
+// Value is the iterator's value_type.
+template< typename It, typename Value >
+struct is_readable_iterator_impl :
+    public std::is_convertible<
+        decltype(*std::declval< It& >()),
+        typename std::add_lvalue_reference< Value >::type
+    >
+{
+};
+
+//
+// void specializations to handle std input and output iterators
+//
+template< typename It >
+struct is_readable_iterator_impl< It, void > :
+    public std::false_type
+{
+};
+
+template< typename It >
+struct is_readable_iterator_impl< It, const void > :
+    public std::false_type
+{
+};
+
+template< typename It >
+struct is_readable_iterator_impl< It, volatile void > :
+    public std::false_type
+{
+};
+
+template< typename It >
+struct is_readable_iterator_impl< It, const volatile void > :
+    public std::false_type
+{
+};
+
+} // namespace detail
+
+template< typename T >
+struct is_readable_iterator :
+    public iterators::detail::is_readable_iterator_impl<
+        T,
+        typename std::iterator_traits< T >::value_type const
+    >::type
+{
+};
+
+} // namespace iterators
+
+using iterators::is_readable_iterator;
+
+} // namespace boost
+
+#endif // IS_READABLE_ITERATOR_DWA2003112_HPP