forked from boostorg/iterator
a little more progress
[SVN r1196]
This commit is contained in:
Jeremy Siek
@@ -127,6 +127,8 @@ adapted and user defined iterators suffer from the well known
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categorisation problems that are inherent to the current iterator
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categories.
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.. _`n1477`: http://anubis.dkuug.dk/JTC1/SC22/WG21/docs/papers/2003/n1477.html
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Though this proposal does not strictly depend on proposal `n1477`_,
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as there is a direct mapping between new and old categories. The proposal
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could be reformulated using this mapping.
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@@ -385,11 +387,11 @@ Header ``<iterator_helper>`` synopsis [lib.iterator.helper.synopsis]
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template <
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class Derived
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, class Value = use_default
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, class Category = use_default
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, class Reference = use_default
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, class Pointer = use_default
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, class Difference = use_default
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, class Value
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, class Category
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, class Reference = Value&
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, class Pointer = Value*
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, class Difference = ptrdiff_t
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>
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class iterator_facade;
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@@ -540,7 +542,7 @@ Class template ``iterator_facade``
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``iterator_facade`` requirements
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--------------------------------
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The ``Derived`` template parameter must be the class deriving from
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The ``Derived`` template parameter must be a derived class of
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``iterator_facade``. The rest of the template parameters specify the
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types for the member typedefs in ``iterator_facade``.
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@@ -601,12 +603,16 @@ interoperable with ``X``.
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:Postconditions:
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:Returns: If ``iterator_category`` is a derived class of
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``readable_lvalue_iterator_tag`` then the return type is ``pointer``
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and the value returned is ``&static_cast<Derived
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const*>(this)->dereference()``. Otherwise a proxy object of
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implementation defined type is returned. The proxy type must have a
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``operator->`` member function with the following signature.
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::
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``readable_lvalue_iterator_tag`` then the return type is ``pointer``
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and the value returned is
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::
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&static_cast<Derived const*>(this)->dereference()
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Otherwise a proxy object is returned. The type of
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the proxy is implementation defined. The proxy class must have
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the following member function.
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::
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const value_type* operator->() const;
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@@ -619,7 +625,21 @@ implementation defined type is returned. The proxy type must have a
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:Requires:
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:Effects:
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:Postconditions:
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:Returns: ``static_cast<Derived const*>(this)->dereference()``
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:Returns: If ``iterator_category`` is a derived class of
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``writable_iterator_tag`` then the return type is
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a proxy object of implementation defined type ``P``
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with the following member functions.
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::
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operator reference();
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P& operator=(value_type const&);
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Otherwise the return type is ``value_type`` and the
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value returned is
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::
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static_cast<Derived const*>(this)->dereference()
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:Throws:
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:Complexity:
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@@ -627,18 +647,24 @@ implementation defined type is returned. The proxy type must have a
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``Derived& operator++();``
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:Requires:
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:Effects:
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:Effects: Invokes the ``increment`` core interface function.
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:Postconditions:
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:Returns: ``static_cast<Derived const*>(this)->dereference();``
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:Returns: ``*this``
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:Throws:
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:Complexity:
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``Derived operator++(int);``
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:Requires:
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:Effects:
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:Effects:
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::
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Derived tmp(static_cast<Derived const*>(this));
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++*this;
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return tmp;
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:Postconditions:
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:Returns: ``static_cast<Derived const*>(this)->dereference();``
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:Returns: A copy of ``*this``.
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:Throws:
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:Complexity:
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@@ -716,7 +742,7 @@ Class template ``iterator_adaptor``
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, class Difference = use_default
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>
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class iterator_adaptor
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: public iterator_facade<Derived, /*impl detail ...*/>
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: public iterator_facade<Derived, /* see details ...*/>
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{
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friend class iterator_core_access;
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public:
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@@ -729,13 +755,10 @@ Class template ``iterator_adaptor``
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{ return *m_iterator; }
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template <
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class OtherDerived, class OtherIterator, class V, class C, class R, class P, class D
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class OtherDerived, class OtherBase, class V, class C, class R, class P, class D
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>
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bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, P, D> const& x) const
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bool equal(iterator_adaptor<OtherDerived, OtherBase, V, C, R, P, D> const& x) const
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{
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BOOST_STATIC_ASSERT(
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(detail::same_category_and_difference<Derived,OtherDerived>::value)
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);
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return m_iterator == x.base();
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}
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void advance(typename super_t::difference_type n)
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@@ -747,14 +770,11 @@ Class template ``iterator_adaptor``
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void decrement() { --m_iterator; }
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template <
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class OtherDerived, class OtherIterator, class V, class C, class R, class P, class D
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class OtherDerived, class OtherBase, class V, class C, class R, class P, class D
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>
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typename super_t::difference_type distance_to(
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iterator_adaptor<OtherDerived, OtherIterator, V, C, R, P, D> const& y) const
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iterator_adaptor<OtherDerived, OtherBase, V, C, R, P, D> const& y) const
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{
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BOOST_STATIC_ASSERT(
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(detail::same_category_and_difference<Derived,OtherDerived>::value)
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);
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return y.base() - m_iterator;
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}
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Base const& base_reference() const
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@@ -768,15 +788,49 @@ Class template ``iterator_adaptor``
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``iterator_adaptor`` requirements
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---------------------------------
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.. Make sure to mention that this works for both old and new
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style iterators. -JGS
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The ``Derived`` template parameter must be a derived class of
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``iterator_adaptor``. The ``Base`` type must implement the expressions
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used in the protected member functions of ``iterator_adaptor`` that
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are not overriden by the ``Derived`` class. The rest of the template
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parameters specify the types for the member typedefs in
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``iterator_facade``. The following pseudo-code specifies the traits
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types for ``iterator_adaptor``.
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::
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if (Value == use_default)
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value_type = iterator_traits<Base>::value_type;
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else
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value_type = remove_cv<Value>::type;
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if (Reference == use_default) {
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if (Value == use_default)
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reference = iterator_traits<Base>::reference;
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else
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reference = Value&;
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} else
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reference = Reference;
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if (Pointer == use_default) {
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if (Value == use_default)
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pointer = iterator_traits<Base>::pointer;
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else
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pointer = Value*;
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} else
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pointer = Pointer;
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if (Category == use_default)
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iterator_category = iterator_traits<Base>::iterator_category;
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else
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iterator_category = Category;
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if (Distance == use_default)
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difference_type = iterator_traits<Base>::difference_type;
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else
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difference_type = Distance;
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.. I'm not sure we should say that in the standard text; let other
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people add non-normative in editing if they feel the need
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;-) -DWA
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.. Well, we have to specify the requirements for the template
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parameters such as ``Category``, so this will come up. -JGS
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Specialized adaptors [lib.iterator.special.adaptors]
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====================================================
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