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185 lines
5.0 KiB
ReStructuredText
185 lines
5.0 KiB
ReStructuredText
.. Version 1.4 of this ReStructuredText document corresponds to
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n1530_, the paper accepted by the LWG for TR1.
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.. Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All
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rights reserved.
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.. parsed-literal::
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template <
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class Derived
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, class Base
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, class Value = use_default
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, class CategoryOrTraversal = use_default
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, class Reference = use_default
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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, *V*, *C*, *R*, *D*> // see details__
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{
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friend class iterator_core_access;
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public:
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iterator_adaptor();
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explicit iterator_adaptor(Base iter);
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Base const base() const;
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protected:
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Base const& base_reference() const;
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Base& base_reference();
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private: // Core iterator interface for iterator_facade.
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typename iterator_adaptor::reference dereference() const;
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template <
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class OtherDerived, class OtherIterator, class V, class C, class R, class D
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>
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bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const;
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void advance(typename iterator_adaptor::difference_type n);
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void increment();
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void decrement();
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template <
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class OtherDerived, class OtherIterator, class V, class C, class R, class D
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>
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typename iterator_adaptor::difference_type distance_to(
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iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const;
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private:
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Base m_iterator; // exposition only
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};
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__ requirements_
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.. _requirements:
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``iterator_adaptor`` requirements
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---------------------------------
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The ``Derived`` template argument must be a publicly derived from
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``iterator_adaptor``.
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The ``Base`` argument shall be Assignable and Copy Constructible.
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.. _base_parameters:
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``iterator_adaptor`` base class parameters
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------------------------------------------
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The *V*, *C*, *R*, and *D* parameters of the ``iterator_facade``
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used as a base class in the summary of ``iterator_adaptor``
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above are defined as follows:
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.. parsed-literal::
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*V* = if (Value is use_default)
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return iterator_traits<Base>::value_type
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else
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return Value
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*C* = if (CategoryOrTraversal is use_default)
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return iterator_traversal<Base>::type
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else
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return CategoryOrTraversal
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*R* = if (Reference is use_default)
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if (Value is use_default)
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return iterator_traits<Base>::reference
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else
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return Value&
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else
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return Reference
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*D* = if (Difference is use_default)
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return iterator_traits<Base>::difference_type
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else
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return Difference
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``iterator_adaptor`` models
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---------------------------
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In order for ``Derived`` to model the iterator concepts corresponding
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to ``iterator_traits<Derived>::iterator_category``, the expressions
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involving ``m_iterator`` in the specifications of those private member
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functions of ``iterator_adaptor`` that may be called by
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``iterator_facade<Derived, V, C, R, D>`` in evaluating any valid
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expression involving ``Derived`` in those concepts' requirements.
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.. The above is confusing and needs a rewrite. -JGS
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``iterator_adaptor`` public operations
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--------------------------------------
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``iterator_adaptor();``
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:Requires: The ``Base`` type must be Default Constructible.
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:Returns: An instance of ``iterator_adaptor`` with
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``m_iterator`` default constructed.
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``explicit iterator_adaptor(Base iter);``
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:Returns: An instance of ``iterator_adaptor`` with
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``m_iterator`` copy constructed from ``iter``.
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``Base const base() const;``
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:Returns: ``m_iterator``
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[Note: specifying ``Base const`` gives implementations license to
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return ``Base const&`` for efficiency's sake. If ``base()``
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returned just ``Base``, it would be possible to call non-``const``
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member functions on the result object directly]
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``iterator_adaptor`` protected member functions
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-----------------------------------------------
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``Base const& base_reference() const;``
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:Returns: A const reference to ``m_iterator``.
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``Base& base_reference();``
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:Returns: A non-const reference to ``m_iterator``.
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``iterator_adaptor`` private member functions
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---------------------------------------------
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``typename iterator_adaptor::reference dereference() const;``
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:Returns: ``*m_iterator``
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::
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template <
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class OtherDerived, class OtherIterator, class V, class C, class R, class D
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>
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bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const;
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:Returns: ``m_iterator == x.base()``
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``void advance(typename iterator_adaptor::difference_type n);``
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:Effects: ``m_iterator += n;``
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``void increment();``
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:Effects: ``++m_iterator;``
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``void decrement();``
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:Effects: ``--m_iterator;``
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::
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template <
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class OtherDerived, class OtherIterator, class V, class C, class R, class D
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>
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typename iterator_adaptor::difference_type distance_to(
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iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const;
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:Returns: ``y.base() - m_iterator``
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