Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Boost
C++ Libraries
...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
| Author: | David Abrahams, Jeremy Siek, Thomas Witt |
|---|---|
| Contact: | dave@boost-consulting.com, jsiek@osl.iu.edu, witt@styleadvisor.com |
| Organization: | Boost Consulting, Indiana University Open Systems Lab, Zephyr Associates, Inc. |
| Date: | 2006-09-11 |
| Copyright: | Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2004. |
| abstract: | The iterator_archetype class constructs a minimal implementation of one of the iterator access concepts and one of the iterator traversal concepts. This is used for doing a compile-time check to see if a the type requirements of a template are really enough to cover the implementation of the template. For further information see the documentation for the boost::concept_check library. |
|---|
Table of Contents
namespace iterator_archetypes
{
// Access categories
typedef /*implementation defined*/ readable_iterator_t;
typedef /*implementation defined*/ writable_iterator_t;
typedef /*implementation defined*/ readable_writable_iterator_t;
typedef /*implementation defined*/ readable_lvalue_iterator_t;
typedef /*implementation defined*/ writable_lvalue_iterator_t;
}
template <
class Value
, class AccessCategory
, class TraversalCategory
>
class iterator_archetype
{
typedef /* see below */ value_type;
typedef /* see below */ reference;
typedef /* see below */ pointer;
typedef /* see below */ difference_type;
typedef /* see below */ iterator_category;
};
The access category types provided correspond to the following standard iterator access concept combinations:
readable_iterator_t := Readable Iterator writable_iterator_t := Writeable Iterator readable_writable_iterator_t := Readable Iterator & Writeable Iterator & Swappable Iterator readable_lvalue_iterator_t := Readable Iterator & Lvalue Iterator writeable_lvalue_iterator_t := Readable Iterator & Writeable Iterator & Swappable Iterator & Lvalue Iterator
The AccessCategory argument must be one of the predefined access category tags. The TraversalCategory must be one of the standard traversal tags. The Value type must satisfy the requirements of the iterator concept specified by AccessCategory and TraversalCategory as implied by the nested traits types.
iterator_archetype models the iterator concepts specified by the AccessCategory and TraversalCategory arguments. iterator_archetype does not model any other access concepts or any more derived traversal concepts.
The nested trait types are defined as follows:
if (AccessCategory == readable_iterator_t)
value_type = Value
reference = Value
pointer = Value*
else if (AccessCategory == writable_iterator_t)
value_type = void
reference = void
pointer = void
else if (AccessCategory == readable_writable_iterator_t)
value_type = Value
reference :=
A type X that is convertible to Value for which the following
expression is valid. Given an object x of type X and v of type
Value.
x = v
pointer = Value*
else if (AccessCategory == readable_lvalue_iterator_t)
value_type = Value
reference = Value const&
pointer = Value const*
else if (AccessCategory == writable_lvalue_iterator_t)
value_type = Value
reference = Value&
pointer = Value*
if ( TraversalCategory is convertible to forward_traversal_tag )
difference_type := ptrdiff_t
else
difference_type := unspecified type
iterator_category :=
A type X satisfying the following two constraints:
1. X is convertible to X1, and not to any more-derived
type, where X1 is defined by:
if (reference is a reference type
&& TraversalCategory is convertible to forward_traversal_tag)
{
if (TraversalCategory is convertible to random_access_traversal_tag)
X1 = random_access_iterator_tag
else if (TraversalCategory is convertible to bidirectional_traversal_tag)
X1 = bidirectional_iterator_tag
else
X1 = forward_iterator_tag
}
else
{
if (TraversalCategory is convertible to single_pass_traversal_tag
&& reference != void)
X1 = input_iterator_tag
else
X1 = output_iterator_tag
}
2. X is convertible to TraversalCategory