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- .. |iterator-category| replace:: *iterator-category*
- .. _iterator-category:
- .. parsed-literal::
-
- *iterator-category*\ (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)
- *the program is ill-formed*
- 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
- && 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
- && R is convertible to V)
- X1 = input_iterator_tag
- else
- X1 = C
- }
- 2. |category-to-traversal|_\ (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.
- .. |category-to-traversal| replace:: *category-to-traversal*
- .. _`category-to-traversal`: new-iter-concepts.html#category-to-traversal
- [Note: the intention is to allow ``iterator_category`` to be one of
- the five original category tags when convertibility to one of the
- traversal tags would add no information]
- .. 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)
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