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rigged new iterator_traits for backward compatibility

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[SVN r9577]
This commit is contained in:
Jeremy Siek
2001-03-18 18:37:49 +00:00
parent cbbe851adb
commit eb06c122d1
3 changed files with 205 additions and 153 deletions
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123
development/boost/iterator_traits.hpp
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@@ -2,21 +2,14 @@
#define BOOST_ITERATOR_TRAITS_HPP
#include <boost/config.hpp>
#include <boost/type_traits.hpp>
#include <boost/type_traits/conversion_traits.hpp>
#include <boost/type_traits/cv_traits.hpp>
#include <boost/pending/ct_if.hpp>
#include <boost/detail/iterator.hpp>
namespace boost {
template <typename Iterator>
struct iterator_traits {
typedef typename Iterator::value_type value_type;
typedef typename Iterator::reference reference;
typedef typename Iterator::pointer pointer;
typedef typename Iterator::difference_type difference_type;
typedef typename Iterator::return_category return_category;
typedef typename Iterator::motion_category motion_category;
};
// Motion Categories
// Traversal Categories
struct single_pass_iterator_tag { };
struct forward_iterator_tag : public single_pass_iterator_tag { };
struct bidirectional_iterator_tag : public forward_iterator_tag { };
@@ -28,29 +21,113 @@ namespace boost {
struct mutable_lvalue_iterator_tag : virtual public writable_iterator_tag,
virtual public readable_iterator_tag { };
struct constant_lvalue_iterator_tag : public readable_iterator_tag { };
#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
struct error_iterator_tag { };
// Inherit from iterator_base if your iterator defines its own
// return_category and traversal_category. Otherwise, the "old style"
// iterator category will be mapped to the return_category and
// traversal_category.
struct new_iterator_base { };
namespace detail {
template <bool IsConst>
struct pointer_return_category {
typedef constant_lvalue_iterator_tag type;
struct iter_traits_from_nested_types {
template <typename Iterator> struct bind {
typedef typename Iterator::value_type value_type;
typedef typename Iterator::reference reference;
typedef typename Iterator::pointer pointer;
typedef typename Iterator::difference_type difference_type;
typedef typename Iterator::return_category return_category;
typedef typename Iterator::traversal_category traversal_category;
};
};
template <>
struct pointer_return_category<false> {
typedef mutable_lvalue_iterator_tag type;
template <typename ValueType>
struct choose_lvalue_return {
typedef typename ct_if<is_const<ValueType>::value,
boost::constant_lvalue_iterator_tag,
boost::mutable_lvalue_iterator_tag>::type type;
};
template <typename Category, typename ValueType>
struct iter_category_to_return {
typedef typename ct_if<
is_convertible<Category*, std::forward_iterator_tag*>::value,
typename choose_lvalue_return<ValueType>::type,
typename ct_if<
is_convertible<Category*, std::input_iterator_tag*>::value,
boost::readable_iterator_tag,
typename ct_if<
is_convertible<Category*, std::output_iterator_tag*>::value,
boost::writable_iterator_tag,
boost::error_iterator_tag
>::type
>::type
>::type type;
};
template <typename Category>
struct iter_category_to_traversal {
typedef typename ct_if<
is_convertible<Category*, std::random_access_iterator_tag*>::value,
boost::random_access_iterator_tag,
typename ct_if<
is_convertible<Category*, std::bidirectional_iterator_tag*>::value,
boost::bidirectional_iterator_tag,
typename ct_if<
is_convertible<Category*, std::forward_iterator_tag*>::value,
boost::forward_iterator_tag,
boost::single_pass_iterator_tag>::type
>::type
>::type type;
};
struct iter_traits_from_old_traits {
template <typename Iterator> class bind {
typedef boost::detail::iterator_traits<Iterator> OldTraits;
typedef typename OldTraits::iterator_category Cat;
public:
typedef typename OldTraits::value_type value_type;
typedef typename OldTraits::reference reference;
typedef typename OldTraits::pointer pointer;
typedef typename OldTraits::difference_type difference_type;
typedef iter_category_to_return<Cat,value_type>::type return_category;
typedef iter_category_to_traversal<Cat>::type traversal_category;
};
};
template <typename Iterator>
class choose_iter_traits {
typedef typename ct_if<is_convertible<Iterator*,
new_iterator_base*>::value,
iter_traits_from_nested_types,
iter_traits_from_old_traits>::type Choice;
public:
typedef typename Choice:: template bind<Iterator> type;
};
} // namespace detail
template <typename Iterator>
class iterator_traits
: public detail::choose_iter_traits<Iterator>::type { };
#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
template <typename T>
struct iterator_traits<T*> {
struct iterator_traits<T*>
{
typedef T value_type;
typedef T& reference;
typedef T* pointer;
typedef std::ptrdiff_t difference_type;
typedef typename detail::pointer_return_category<is_const<T>::value>::type
typedef typename ct_if<is_const<T>::value,
boost::constant_lvalue_iterator_tag,
boost::mutable_lvalue_iterator_tag>::type
return_category;
typedef random_access_iterator_tag motion_category;
typedef boost::random_access_iterator_tag traversal_category;
};
#endif