Re: [boost] iterator adaptors and operator[]

From: Yitzhak Sapir (yitzhaks_at_[hidden])
Date: 2002-09-05 15:35:33

On Thu, 5 Sep 2002, David Abrahams wrote:

> From: "Yitzhak Sapir" <yitzhaks_at_[hidden]>
>
> <<The attached patch solves it using inheritance (operator[] is inherited,
> with the inherited class chosen based on Category), but is much more
> complex than the above trick would have been.>>
>
> Does it pass all the regression tests?

No.  But the following patch almost does (for MSVC and MSVC+STLPort):

Given:
run libs/utility/counting_iterator_test.cpp
run libs/utility/iterator_adaptor_test.cpp
run libs/utility/transform_iterator_test.cpp
run libs/utility/indirect_iterator_test.cpp
run libs/utility/iter_traits_gen_test.cpp
compile-fail libs/utility/iter_adaptor_fail_expected1.cpp
compile-fail libs/utility/iter_adaptor_fail_expected2.cpp
run libs/utility/iterator_traits_test.cpp
run libs/utility/iterators_test.cpp

It fails for iterators_test.cpp alone:

*** libs/utility/iterators_test.cpp ***

** Microsoft Visual C++
cl /Feboosttmp.exe /nologo /Zm400 /MDd /W3 /GR /GX /Zi /Od /GZ /I".." /D "WIN32" /D "_DEBUG" /D "_MBCS" /D "_CONSOLE" ../libs/utility/iterators_test.cpp /link /incremental:no user32.lib
iterators_test.cpp
..\boost/test/unit_test_log.hpp(20) : fatal error C1083: Cannot open include file: 'boost/test/detail/unit_test_config.hpp': No such file or directory
0.14 s

Return code: 2
Fail

** Microsoft Visual C++ with STLport
cl /Feboosttmp.exe /nologo /Zm400 /MDd /W3 /GR /GX /Zi /Od /GZ /I "$BOOST_STLPORT_PATH/include/stlport" /I".." /D "__STL_DEBUG" /D "WIN32" /D "_DEBUG" /D "_MBCS" /D "_CONSOLE" ../libs/utility/iterators_test.cpp /link /incremental:no user32.lib
iterators_test.cpp
..\boost/test/unit_test_log.hpp(20) : fatal error C1083: Cannot open include file: 'boost/test/detail/unit_test_config.hpp': No such file or directory
0.05 s

Return code: 2
Fail

cvs -z9 -Q diff -c boost/iterator_adaptors.hpp
Index: boost/iterator_adaptors.hpp
===================================================================
RCS file: /cvsroot/boost/boost/boost/iterator_adaptors.hpp,v
retrieving revision 1.65
diff -c -r1.65 iterator_adaptors.hpp
*** boost/iterator_adaptors.hpp	8 Aug 2002 16:42:18 -0000	1.65
--- boost/iterator_adaptors.hpp	5 Sep 2002 19:24:36 -0000
***************
*** 557,562 ****
--- 557,565 ----
    typedef detail::cons_type<detail::iterator_category_tag, IteratorCategory> type;
  };

+ template <class Base, class Policies, class Value, class Reference, class Pointer, class Category, class Distance>
+ struct iterator_adaptor;
+
  namespace detail {

    struct end_of_list { };
***************
*** 761,769 ****

        BOOST_STATIC_ASSERT(forward_iter_with_real_reference);
    };
- } // namespace detail

  // This macro definition is only temporary in this file
  # if !defined(BOOST_MSVC) || BOOST_MSVC > 1300
--- 764,866 ----

        BOOST_STATIC_ASSERT(forward_iter_with_real_reference);
    };

+   struct non_random_access_index_iterator_base
+   {
+ 	  template <class Base, class Policies, class Value, class Reference, class Pointer, class Category, class Distance>
+ 	  struct index_base_type
+ 		  : detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance>::type
+ 	  {
+ 		 protected:
+ 			typedef iterator_adaptor<Base,Policies,Value,Reference,Pointer,Category,Distance> self;
+ 		 public:
+ 			typedef detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance> TraitsGen;
+ 			typedef typename TraitsGen::type Traits;
+
+ 			typedef typename Traits::difference_type difference_type;
+ 			typedef typename Traits::value_type value_type;
+ 			typedef typename Traits::pointer pointer;
+ 			typedef typename Traits::reference reference;
+ 			typedef typename Traits::iterator_category iterator_category;
+
+ 			typedef Base base_type;
+ 			typedef Policies policies_type;
+ 	  };
+   };
+
+   struct random_access_index_iterator_base
+   {
+ 	  template <class Base, class Policies, class Value, class Reference, class Pointer, class Category, class Distance>
+ 	  struct index_base_type
+ 		  : detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance>::type
+ 	  {
+ 		 protected:
+ 			typedef iterator_adaptor<Base,Policies,Value,Reference,Pointer,Category,Distance> self;
+ 		 public:
+ 			typedef detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance> TraitsGen;
+ 			typedef typename TraitsGen::type Traits;
+
+ 			typedef typename Traits::difference_type difference_type;
+ 			typedef typename Traits::value_type value_type;
+ 			typedef typename Traits::pointer pointer;
+ 			typedef typename Traits::reference reference;
+ 			typedef typename Traits::iterator_category iterator_category;
+
+ 			typedef Base base_type;
+ 			typedef Policies policies_type;
+
+ 			value_type operator[](difference_type n) const
+ 				{ return *(*static_cast<const iterator_adaptor<Base,Policies,Value,Reference,Pointer,Category, Distance>*>(this) + n); }
+ 	  };
+   };
+
+   template <class Category> struct index_category_chooser
+   {
+ 	  struct iterator_base
+ 	  {
+ 		  template <class Base, class Policies, class Value, class Reference, class Pointer, class Category, class Distance>
+ 		  struct index_base_type;
+ 	  };
+   };
+
+   template<> struct index_category_chooser<std::input_iterator_tag>
+   {
+ 	  typedef non_random_access_index_iterator_base iterator_base;
+   };

+   template<> struct index_category_chooser<std::output_iterator_tag>
+   {
+ 	  typedef non_random_access_index_iterator_base iterator_base;
+   };
+
+   template<> struct index_category_chooser<std::forward_iterator_tag>
+   {
+ 	  typedef non_random_access_index_iterator_base iterator_base;
+   };
+
+   template<> struct index_category_chooser<std::bidirectional_iterator_tag>
+   {
+ 	  typedef non_random_access_index_iterator_base iterator_base;
+   };
+
+   template<> struct index_category_chooser<std::random_access_iterator_tag>
+   {
+ 	  typedef random_access_index_iterator_base iterator_base;
+ //	  typedef non_random_access_index_iterator_base iterator_base;
+   };
+
+   template  <class Base, class Policies, class Value, class Reference, class Pointer, class Category, class Distance>
+ 	   struct index_iterator_impl
+   {
+ 		typedef detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance> TraitsGen;
+ 		typedef typename TraitsGen::type Traits;
+
+ 		typedef typename Traits::iterator_category iterator_category;
+ 	  typedef index_category_chooser<iterator_category>::iterator_base iterator_base_generator;
+ 	  typedef iterator_base_generator::index_base_type<Base,Policies,Value,Reference,Pointer,Category,Distance> type;
+   };
+
+ } // namespace detail

  // This macro definition is only temporary in this file
  # if !defined(BOOST_MSVC) || BOOST_MSVC > 1300
***************
*** 811,835 ****
  #ifdef BOOST_RELOPS_AMBIGUITY_BUG
      iterator_comparisons<
            iterator_adaptor<Base,Policies,Value,Reference,Pointer,Category,Distance>,
!     typename detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category, Distance>::type
   >
  #else
!     detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance>::type
  #endif
  {
!     typedef iterator_adaptor<Base,Policies,Value,Reference,Pointer,Category,Distance> self;
   public:
!     typedef detail::iterator_adaptor_traits_gen<Base,Value,Reference,Pointer,Category,Distance> TraitsGen;
!     typedef typename TraitsGen::type Traits;

!     typedef typename Traits::difference_type difference_type;
!     typedef typename Traits::value_type value_type;
!     typedef typename Traits::pointer pointer;
!     typedef typename Traits::reference reference;
!     typedef typename Traits::iterator_category iterator_category;

!     typedef Base base_type;
!     typedef Policies policies_type;

   private:
      typedef detail::validator<
--- 908,934 ----
  #ifdef BOOST_RELOPS_AMBIGUITY_BUG
      iterator_comparisons<
            iterator_adaptor<Base,Policies,Value,Reference,Pointer,Category,Distance>,
! 	typename detail::index_iterator_impl<Base,Policies,Value,Reference,Pointer,Category, Distance>::type
   >
  #else
! 	detail::index_iterator_impl<Base,Policies,Value,Reference,Pointer,Category,Distance>::type
  #endif
  {
! 	typedef detail::index_iterator_impl<Base,Policies,Value,Reference,Pointer,Category,Distance>::type
! 		index_base_type;
! 	typedef typename index_base_type::self self;
   public:
! 	typedef index_base_type::TraitsGen TraitsGen;
! 	typedef index_base_type::Traits Traits;

! 	typedef typename index_base_type::difference_type difference_type;
! 	typedef typename index_base_type::value_type value_type;
! 	typedef typename index_base_type::pointer pointer;
! 	typedef typename index_base_type::reference reference;
! 	typedef typename index_base_type::iterator_category iterator_category;

! 	typedef index_base_type::base_type base_type;
! 	typedef index_base_type::policies_type policies_type;

   private:
      typedef detail::validator<
***************
*** 879,887 ****
  #ifdef BOOST_MSVC
  # pragma warning(pop)
  #endif
-
-     value_type operator[](difference_type n) const
-         { return *(*this + n); }

      self& operator++() {
  #if !defined(__MWERKS__) || __MWERKS__ >= 0x2405
--- 978,983 ----

*****CVS exited normally with code 1*****