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Dave Abrahams
2004-01-18 19:56:39 +00:00
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Index: facade-and-adaptor.rst
===================================================================
RCS file: /cvsroot/boost/boost/libs/iterator/doc/facade-and-adaptor.rst,v
retrieving revision 1.9
retrieving revision 1.14
diff -b -d -u -r1.9 -r1.14
--- facade-and-adaptor.rst 22 Sep 2003 19:55:00 -0000 1.9
+++ facade-and-adaptor.rst 18 Jan 2004 15:51:06 -0000 1.14
@@ -3,17 +3,25 @@ None
+++++++++++++++++++++++++++++
:Author: David Abrahams, Jeremy Siek, Thomas Witt
-:Contact: dave@boost-consulting.com, jsiek@osl.iu.edu, witt@acm.org
+:Contact: dave@boost-consulting.com, jsiek@osl.iu.edu, witt@styleadvisor.com
:organization: `Boost Consulting`_, Indiana University `Open Systems
- Lab`_, University of Hanover `Institute for Transport
- Railway Operation and Construction`_
-:date: $Date: 2004/01/18 19:56:39 $
-:Number: N1530=03-0113
+ Lab`_, `Zephyr Associates, Inc.`_
+:date: $Date: 2004/01/18 19:56:39 $
+
+:Number: This is a revised version of N1530_\ =03-0113, which was
+ accepted for Technical Report 1 by the C++ standard
+ committee's library working group.
+
+.. Version 1.9 of this ReStructuredText document corresponds to
+ n1530_, the paper accepted by the LWG.
+
+.. _n1530: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/papers/2003/n1530.html
+
:copyright: Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved
.. _`Boost Consulting`: http://www.boost-consulting.com
.. _`Open Systems Lab`: http://www.osl.iu.edu
-.. _`Institute for Transport Railway Operation and Construction`: http://www.ive.uni-hannover.de
+.. _`Zephyr Associates, Inc.`: http://www.styleadvisor.com
:abstract: We propose a set of class templates that help programmers
build standard-conforming iterators, both from scratch and
@@ -124,15 +132,15 @@ None
=================
This proposal is formulated in terms of the new ``iterator concepts``
-as proposed in `n1477`_, since user-defined and especially adapted
+as proposed in n1550_, since user-defined and especially adapted
iterators suffer from the well known categorization problems that are
inherent to the current iterator categories.
-.. _`n1477`: http://anubis.dkuug.dk/JTC1/SC22/WG21/docs/papers/2003/n1477.html
+.. _n1550: http://anubis.dkuug.dk/JTC1/SC22/WG21/docs/papers/2003/n1550.html
-This proposal does not strictly depend on proposal `n1477`_, as there
+This proposal does not strictly depend on proposal n1550_, as there
is a direct mapping between new and old categories. This proposal
-could be reformulated using this mapping if `n1477`_ was not accepted.
+could be reformulated using this mapping if n1550_ was not accepted.
Interoperability
================
@@ -141,24 +149,24 @@ None
current standard. There are currently two defect reports that are
concerned with interoperability issues.
-Issue `179`_ concerns the fact that mutable container iterator types
+Issue 179_ concerns the fact that mutable container iterator types
are only required to be convertible to the corresponding constant
iterator types, but objects of these types are not required to
interoperate in comparison or subtraction expressions. This situation
is tedious in practice and out of line with the way built in types
work. This proposal implements the proposed resolution to issue
-`179`_, as most standard library implementations do nowadays. In other
+179_, as most standard library implementations do nowadays. In other
words, if an iterator type A has an implicit or user defined
conversion to an iterator type B, the iterator types are interoperable
and the usual set of operators are available.
-Issue `280`_ concerns the current lack of interoperability between
+Issue 280_ concerns the current lack of interoperability between
reverse iterator types. The proposed new reverse_iterator template
fixes the issues raised in 280. It provides the desired
interoperability without introducing unwanted overloads.
-.. _`179`: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-defects.html#179
-.. _`280`: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-active.html#280
+.. _179: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-defects.html#179
+.. _280: http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-active.html#280
Iterator Facade
@@ -195,7 +203,7 @@ None
* ``filter_iterator``, which provides a view of an iterator range in
which some elements of the underlying range are skipped.
-.. _counting_iterator:
+.. _counting:
* ``counting_iterator``, which adapts any incrementable type
(e.g. integers, iterators) so that incrementing/decrementing the
@@ -226,15 +234,13 @@ Issue 9.1 et al
::
struct use_default;
- const unsigned use_default_access = -1;
struct iterator_core_access { /* implementation detail */ };
template <
class Derived
, class Value
- , unsigned AccessCategory
- , class TraversalCategory
+ , class CategoryOrTraversal
, class Reference = Value&
, class Difference = ptrdiff_t
>
@@ -244,8 +250,7 @@ Issue 9.1 et al.
class Derived
, class Base
, class Value = use_default
- , unsigned Access = use_default_access
- , class Traversal = use_default
+ , class CategoryOrTraversal = use_default
, class Reference = use_default
, class Difference = use_default
>
@@ -254,10 +259,9 @@ Issue 9.1 et al.
template <
class Iterator
, class Value = use_default
- , unsigned Access = use_default_access
- , class Traversal = use_default
+ , class CategoryOrTraversal = use_default
, class Reference = use_default
, class Difference = use_default
>
class indirect_iterator;
Issue 9.44y
+ template <class Dereferenceable>
+ struct pointee;
+
+ template <class Dereferenceable>
+ struct indirect_reference;
+
template <class Iterator>
class reverse_iterator;
@@ -277,8 +287,7 @@ Issue 9.1 et al.
template <
class Incrementable
- , unsigned Access = use_default_access
- , class Traversal = use_default
+ , class CategoryOrTraversal = use_default
, class Difference = use_default
>
class counting_iterator
@@ -312,17 +321,35 @@ Issue 9.8
Specialized adaptors [lib.iterator.special.adaptors]
====================================================
-.. The requirements for all of these need to be written *much* more
- formally -DWA
-
-[*Note:* The ``enable_if_convertible<X,Y>::type`` expression used in
+The ``enable_if_convertible<X,Y>::type`` expression used in
this section is for exposition purposes. The converting constructors
for specialized adaptors should be only be in an overload set provided
that an object of type ``X`` is implicitly convertible to an object of
-type ``Y``. The ``enable_if_convertible`` approach uses SFINAE to
+type ``Y``.
+The signatures involving ``enable_if_convertible`` should behave
+*as-if* ``enable_if_convertible`` were defined to be::
+
+ template <bool> enable_if_convertible_impl
+ {};
+
+ template <> enable_if_convertible_impl<true>
+ { struct type; };
+
+ template<typename From, typename To>
+ struct enable_if_convertible
+ : enable_if_convertible_impl<is_convertible<From,To>::value>
+ {};
+
+If an expression other than the default argument is used to supply
+the value of a function parameter whose type is written in terms
+of ``enable_if_convertible``, the program is ill-formed, no
+diagnostic required.
+
+[*Note:* The ``enable_if_convertible`` approach uses SFINAE to
take the constructor out of the overload set when the types are not
-implicitly convertible.]
+implicitly convertible.
+]
Indirect iterator
@@ -330,6 +357,16 @@ Issue 9.44y
.. include:: indirect_iterator_abstract.rst
+Class template ``pointee``
+....................................
+
+.. include:: pointee_ref.rst
+
+Class template ``indirect_reference``
+.....................................
+
+.. include:: indirect_reference_ref.rst
+
Class template ``indirect_iterator``
....................................
@@ -393,8 +430,7 @@
-..
- LocalWords: Abrahams Siek Witt istream ostream iter MTL strided interoperate
+.. LocalWords: Abrahams Siek Witt istream ostream iter MTL strided interoperate
LocalWords: CRTP metafunctions inlining lvalue JGS incrementable BGL LEDA cv
LocalWords: GraphBase struct ptrdiff UnaryFunction const int typename bool pp
LocalWords: lhs rhs SFINAE markup iff tmp OtherDerived OtherIterator DWA foo