| Author: | David Abrahams, Jeremy Siek, Thomas Witt |
|---|---|
| Contact: | dave@boost-consulting.com, jsiek@osl.iu.edu, witt@ive.uni-hannover.de |
| Organization: | Boost Consulting, Indiana University Open Systems Lab, University of Hanover Institute for Transport Railway Operation and Construction |
| Date: | 2003-09-14 |
| Copyright: | Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved |
| abstract: |
|---|
The indirect iterator adapts an iterator by applying an extra dereference inside of operator*(). For example, this iterator adaptor makes it possible to view a container of pointers (e.g. list<foo*>) as if it were a container of the pointed-to type (e.g. list<foo>) .
template <
class Iterator
, class Value = use_default
, class Category = use_default
, class Reference = use_default
, class Difference = use_default
>
class indirect_iterator
: public iterator_adaptor</* see discussion */>
{
friend class iterator_core_access;
public:
indirect_iterator();
indirect_iterator(Iterator x);
template <
class Iterator2, class Value2, class Category2
, class Reference2, class Difference2
>
indirect_iterator(
indirect_iterator<
Iterator2, Value2, Category2, Reference2, Difference2
> const& y
, typename enable_if_convertible<Iterator2, Iterator>::type* = 0 // exposition
);
private: // as-if specification
typename indirect_iterator::reference dereference() const
{
return **this->base();
}
};
The value_type of the Iterator template parameter should itself be dereferenceable. The return type of the operator* for the value_type must be the same type as the Reference template parameter. The Value template parameter will be the value_type for the indirect_iterator, unless Value is const. If Value is const X, then value_type will be non- const X. The default for Value is
iterator_traits< iterator_traits<Iterator>::value_type >::value_type
If the default is used for Value, then there must be a valid specialization of iterator_traits for the value type of the base iterator.
The Reference parameter will be the reference type of the indirect_iterator. The default is Value&.
The Category parameter is the iterator_category type for the indirect_iterator. The default is iterator_traits<Iterator>::iterator_category.
The indirect iterator will model the most refined standard traversal concept that is modeled by the Iterator type. The indirect iterator will model the most refined standard access concept that is modeled by the value type of Iterator.
indirect_iterator();
| Requires: | Iterator must be Default Constructible. |
|---|---|
| Returns: | An instance of indirect_iterator with a default constructed base object. |
indirect_iterator(Iterator x);
| Returns: | An instance of indirect_iterator with the iterator_adaptor subobject copy constructed from x. |
|---|
template <
class Iterator2, class Value2, class Category2
, class Reference2, class Difference2
>
indirect_iterator(
indirect_iterator<
Iterator2, Value2, Category2, Reference2, Difference2
> const& y
, typename enable_if_convertible<Iterator2, Iterator>::type* = 0 // exposition
);
| Requires: | Iterator2 is implicitly convertible to Iterator. |
|---|---|
| Returns: | An instance of indirect_iterator that is a copy of y. |