feedc0de/boost_iterator
1
0
Fork 0
forked from boostorg/iterator
Code Pull Requests Activity

Fixed up definition of facade's iterator_category

Browse Source 
fixed table widths in new-iter-concepts

cross-referenced interoperability concept in iterator_facade_tutorial

iterator_traversal can't satisfy UnaryTypeTrait: that's a boolean trait.


[SVN r21742]
This commit is contained in:
Dave Abrahams
2004-01-14 23:23:54 +00:00
parent 42147b9e86
commit f1f6262be7
7 changed files with 394 additions and 318 deletions
Download Patch File Download Diff File Expand all files Collapse all files

65
doc/facade-and-adaptor.html
View File

@ -693,28 +693,53 @@ template <class Derived, class V, class TC, class R, class D>
Derived operator+ (iterator_facade<Derived, V, TC, R, D> const&,
typename Derived::difference_type n)
</pre>
<a class="target" id="iterator-category" name="iterator-category"></a><p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">iterator_facade</span></tt> is
<tt class="literal"><span class="pre">facade_iterator_category(CategoryOrTraversal,</span> <span class="pre">value_type,</span>
<span class="pre">reference)</span></tt>, as specified by the following pseudo-code:</p>
<a class="target" id="iterator-category" name="iterator-category"></a><p>The <tt class="literal"><span class="pre">iterator_category</span></tt> member of <tt class="literal"><span class="pre">iterator_facade</span></tt> is</p>
<pre class="literal-block">
facade_iterator_category(C, V, R) =
if (C is convertible to input_iterator_tag or output_iterator_tag) then
return C
else if (C is convertible to incrementable_traversal_tag) then
if (R is a reference type
and C is convertible to forward_traversal_tag) then
if (C is convertible to random_access_traversal_tag)
return a type convertible to random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
return a type convertible to bidirectional_iterator_tag
else
return a type convertible to forward_iterator_tag
else if (C is convertible to single_pass_traversal_tag
and R is convertible to V)
return a type convertible to input_iterator_tag
else
return C
<em>iterator-category</em>(CategoryOrTraversal, value_type, reference)
</pre>
<p>where <em>iterator-category</em> is defined as follows:</p>
<pre class="literal-block">
<em>iterator-category</em>(C,R,V) :=
if (C is convertible to std::input_iterator_tag
|| C is convertible to std::output_iterator_tag
)
return C
else if (C is not convertible to incrementable_traversal_tag)
<em>the program is ill-formed</em>
else return 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 (R is a reference type
&amp;&amp; C is convertible to forward_traversal_tag)
{
if (C is convertible to random_access_traversal_tag)
X1 = random_access_iterator_tag
else if (C is convertible to bidirectional_traversal_tag)
X1 = bidirectional_iterator_tag
else
X1 = forward_iterator_tag
}
else
{
if (C is convertible to single_pass_traversal_tag
&amp;&amp; R is convertible to V)
X1 = input_iterator_tag
else
X1 = C
}
2. <a class="reference" href="new-iter-concepts.html#category-to-traversal"><em>category-to-traversal</em></a>(X) is convertible to the most
derived traversal tag type to which X is also
convertible, and not to any more-derived traversal tag
type.
</pre>
<p>[Note: the intention is to allow <tt class="literal"><span class="pre">iterator_category</span></tt> to be one of
the five original category tags when convertibility to one of the
traversal tags would add no information]</p>
<!-- Copyright David Abrahams 2004. Use, modification and distribution is -->
<!-- subject to 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) -->