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- .. Distributed under the Boost
- .. Software License, Version 1.0. (See accompanying
- .. file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
- .. Version 1.2 of this ReStructuredText document corresponds to
- n1530_, the paper accepted by the LWG for TR1.
- .. Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003.
- The ``iterator_adaptor`` class template adapts some ``Base`` [#base]_
- type to create a new iterator. Instantiations of ``iterator_adaptor``
- are derived from a corresponding instantiation of ``iterator_facade``
- and implement the core behaviors in terms of the ``Base`` type. In
- essence, ``iterator_adaptor`` merely forwards all operations to an
- instance of the ``Base`` type, which it stores as a member.
- .. [#base] The term "Base" here does not refer to a base class and is
- not meant to imply the use of derivation. We have followed the lead
- of the standard library, which provides a base() function to access
- the underlying iterator object of a ``reverse_iterator`` adaptor.
- The user of ``iterator_adaptor`` creates a class derived from an
- instantiation of ``iterator_adaptor`` and then selectively
- redefines some of the core member functions described in the
- ``iterator_facade`` core requirements table. The ``Base`` type need
- not meet the full requirements for an iterator; it need only
- support the operations used by the core interface functions of
- ``iterator_adaptor`` that have not been redefined in the user's
- derived class.
- Several of the template parameters of ``iterator_adaptor`` default
- to ``use_default``. This allows the
- user to make use of a default parameter even when she wants to
- specify a parameter later in the parameter list. Also, the
- defaults for the corresponding associated types are somewhat
- complicated, so metaprogramming is required to compute them, and
- ``use_default`` can help to simplify the implementation. Finally,
- the identity of the ``use_default`` type is not left unspecified
- because specification helps to highlight that the ``Reference``
- template parameter may not always be identical to the iterator's
- ``reference`` type, and will keep users from making mistakes based on
- that assumption.
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