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Added support for more of the traits members where possible, making this useful as a replacement for std::iterator_traits<T> when used as a default template parameter.

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[SVN r9002]
This commit is contained in:
Dave Abrahams 2001-02-07 16:43:57 +00:00 committed by Peter Dimov
parent 88d0434450
commit aa95310651
1 changed files with 46 additions and 14 deletions
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60
include/boost/detail/iterator.hpp
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@ -12,10 +12,20 @@
//
// ...for all compilers and iterators
//
// Additionally, if partial specialization is supported or X is not a pointer
// std::iterator_traits<X>::value_type
//
// And if partial specialization is supported or (X is not a pointer and the
// library isn't the VC6 standard library),
// std::iterator_traits<X>::pointer
// std::iterator_traits<X>::reference
// See http://www.boost.org for most recent version including documentation.
// Revision History
// 07 Feb 2001 - Support for more of the traits members where possible, making
// this useful as a replacement for std::iterator_traits<T> when
// used as a default template parameter.
// 06 Feb 2001 - Removed useless #includes of standard library headers
// (David Abrahams)
@ -49,8 +59,10 @@ namespace boost { namespace detail {
using std::iterator_traits;
using std::distance;
# else
// Workarounds for less-capable implementations
template <bool is_ptr> struct iterator_traits_select;
template <> struct iterator_traits_select<true>
{
template <class Ptr>
@ -95,23 +107,33 @@ struct iterator_category_select
# endif
# ifdef BOOST_BAD_OUTPUT_ITERATOR_SPECIALIZATION
template <bool is_bad_output_iterator> struct bad_difference_select;
template <bool is_bad_output_iterator> struct bad_output_iterator_select;
template <>
struct bad_difference_select<true>
struct bad_output_iterator_select<true>
{
template <class Iterator>
struct difference { typedef void type; };
struct non_category_traits {
typedef void value_type;
typedef void difference_type;
typedef void pointer;
typedef void reference;
};
};
template <>
struct bad_difference_select<false>
struct bad_output_iterator_select<false>
{
template <class Iterator>
struct difference { typedef typename Iterator::difference_type type; };
struct non_category_traits {
typedef typename Iterator::value_type value_type;
typedef typename Iterator::difference_type difference_type;
typedef typename Iterator::pointer pointer;
typedef typename Iterator::reference reference;
};
};
yes_result bad_output_iterator_helper(std::iterator<std::output_iterator_tag,void,void,void,void>*);
no_result bad_output_iterator_helper(...);
# endif
template <class T> struct undefined;
template <> struct iterator_traits_select<false>
{
template <class Iterator>
@ -120,17 +142,24 @@ template <> struct iterator_traits_select<false>
{
# if defined(BOOST_MSVC) && !defined(__SGI_STL_PORT)
typedef typename Iterator::distance_type difference_type;
typedef typename Iterator::value_type value_type;
# elif !defined(BOOST_BAD_OUTPUT_ITERATOR_SPECIALIZATION)
typedef typename Iterator::difference_type difference_type;
typedef typename Iterator::value_type value_type;
typedef typename Iterator::difference_type difference_type;
typedef typename Iterator::pointer pointer;
typedef typename Iterator::reference reference;
# else
private:
// static Iterator *p;
typedef bad_difference_select<
typedef bad_output_iterator_select<
is_convertible<const volatile Iterator*,
const volatile std::iterator<std::output_iterator_tag,void,void,void,void>*
>::value> difference_type_select;
>::value> non_category_traits_select;
typedef non_category_traits_select::template non_category_traits<Iterator> non_category_traits;
public:
typedef typename difference_type_select::template difference<Iterator>::type difference_type;
typedef typename non_category_traits::value_type value_type;
typedef typename non_category_traits::difference_type difference_type;
typedef typename non_category_traits::pointer pointer;
typedef typename non_category_traits::reference reference;
# endif
# if !defined(BOOST_BAD_CONTAINER_ITERATOR_CATEGORY_TYPEDEF)
@ -149,11 +178,14 @@ template <> struct iterator_traits_select<false>
template <class Iterator>
struct iterator_traits
: iterator_traits_select<is_pointer<remove_cv<Iterator>::type>::value>::template traits<Iterator>
{
private:
typedef iterator_traits_select<is_pointer<remove_cv<Iterator>::type>::value> select;
typedef typename select::template traits<Iterator> traits;
typedef typename iterator_traits_select<
is_pointer<remove_cv<Iterator>::type>::value>::template traits<Iterator> traits;
public:
// Why do I need to define these typedefs? It keeps MSVC happy somehow.
// Why don't I need to define the other typedefs? Who knows?!?
typedef typename traits::difference_type difference_type;
typedef typename traits::iterator_category iterator_category;
};