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[range] - Improved default Reference type deduction for the join_iterator as implemented by aschoedl in Trac issue 5061.

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[SVN r70041]
This commit is contained in:
Neil Groves
2011-03-16 23:55:25 +00:00
parent c6a6a46db4
commit f8bb8aafbf
1 changed files with 29 additions and 1 deletions
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30
include/boost/range/detail/join_iterator.hpp
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@ -5,6 +5,9 @@
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// Acknowledgements:
// aschoedl contributed an improvement to the determination
// of the Reference type parameter.
//
// For more information, see http://www.boost.org/libs/range/
//
@ -120,7 +123,32 @@ private:
template<typename Iterator1
, typename Iterator2
, typename ValueType = typename iterator_value<Iterator1>::type
, typename Reference = typename iterator_reference<Iterator1>::type
// find least demanding, commonly supported reference type, in the order &, const&, and by-value:
, typename Reference = typename mpl::if_c<
!is_reference<typename iterator_reference<Iterator1>::type>::value
|| !is_reference<typename iterator_reference<Iterator2>::type>::value,
typename remove_const<
typename remove_reference<
typename iterator_reference<Iterator1>::type
>::type
>::type,
typename mpl::if_c<
is_const<
typename remove_reference<
typename iterator_reference<Iterator1>::type
>::type
>::value
|| is_const<
typename remove_reference<
typename iterator_reference<Iterator2>::type
>::type
>::value,
typename add_const<
typename iterator_reference<Iterator2>::type
>::type,
typename iterator_reference<Iterator1>::type
>::type
>::type
, typename Traversal = typename demote_iterator_traversal_tag<
typename iterator_traversal<Iterator1>::type
, typename iterator_traversal<Iterator2>::type>::type