42 lines
1.1 KiB
C++
42 lines
1.1 KiB
C++
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/*
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* https://www.boost.org/LICENSE_1_0.txt)
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*
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* Copyright (c) 2025 Andrey Semashev
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*/
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#ifndef BOOST_ITERATOR_DETAIL_IF_DEFAULT_HPP_INCLUDED_
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#define BOOST_ITERATOR_DETAIL_IF_DEFAULT_HPP_INCLUDED_
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#include <boost/core/use_default.hpp>
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namespace boost {
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namespace iterators {
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namespace detail {
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// If T is use_default, return Default, otherwise - Nondefault.
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// By default, Nondefault is T, which means
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// the metafunction can be called with just two parameters
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// and in that case will return either T or Default.
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template< typename T, typename Default, typename Nondefault = T >
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struct if_default
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{
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using type = Nondefault;
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};
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template< typename Default, typename Nondefault >
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struct if_default< use_default, Default, Nondefault >
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{
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using type = Default;
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};
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template< typename T, typename Default, typename Nondefault = T >
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using if_default_t = typename if_default< T, Default, Nondefault >::type;
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} // namespace detail
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} // namespace iterators
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} // namespace boost
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#endif // BOOST_ITERATOR_DETAIL_IF_DEFAULT_HPP_INCLUDED_
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