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5906d9c316
- Construct from elements is enabled iff each argument is_convertible to
corresponding element.
- Construct from sequence is enabled iff the single argument is a fusion
sequence.
- C++11 vector and tuple also disable construct from sequence that are
shorter than the destination. C++03 gives incorrect is_convertible
responses in this situation and fails to compile if that constructor is
used; C++11 can have instantation errors in
and_<is_convertible<U, T>...> without the additional check.
- C++11 tuple and vector support truncation conversion and assignment like
all other sequences.
87 lines
3.4 KiB
C++
87 lines
3.4 KiB
C++
/*=============================================================================
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Copyright (c) 2016 Lee Clagett
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#include <boost/detail/lightweight_test.hpp>
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#include <boost/fusion/container/vector.hpp>
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#include <boost/fusion/tuple/tuple.hpp>
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#include <boost/config.hpp>
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#include <boost/type_traits/is_constructible.hpp>
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#include <boost/type_traits/is_convertible.hpp>
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#define FUSION_SEQUENCE boost::fusion::tuple
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#define FUSION_ALT_SEQUENCE boost::fusion::vector
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#include "traits.hpp"
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struct not_convertible {};
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/* Some construction differences in fusion::tuple from std::tuple:
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- Construction from elements cannot call an explicit constructor.
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- There is no implicit construction from elements.
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- Construction from std::pair is _enabled_ when tuple is not of size 2.
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- Construction from tuple is _enabled_ when destination tuple is of
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different size.
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- Implicit construction from std::pair can call explicit constructors on
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elements.
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- Implicit construction from tuple can call explicit constructors on
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elements.
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These differences are historical. Matching the behavior of std::tuple
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could break existing code, however, switching to fusion::vector would
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restore the historical behavior. */
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int
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main()
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{
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using namespace boost::fusion;
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test_convertible(false /* no conversion construction */ );
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BOOST_TEST((is_convertible<std::pair<int, int>, tuple<int, int> >(true)));
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BOOST_TEST((
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is_convertible<std::pair<int, int>, tuple<convertible, int> >(true)
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));
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BOOST_TEST((
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is_convertible<std::pair<int, int>, tuple<int, convertible> >(true)
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));
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BOOST_TEST((
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is_convertible<
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std::pair<int, int>, tuple<convertible, convertible>
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>(true)
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));
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#if defined(FUSION_TEST_HAS_CONSTRUCTIBLE)
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test_constructible();
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BOOST_TEST((is_constructible< tuple<> >(true)));
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BOOST_TEST((is_constructible<tuple<>, int>(false)));
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BOOST_TEST((is_constructible< tuple<int> >(true)));
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BOOST_TEST((is_constructible<tuple<int>, int>(true)));
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BOOST_TEST((is_constructible<tuple<convertible>, int>(true)));
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BOOST_TEST((is_constructible<tuple<not_convertible>, int>(false)));
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BOOST_TEST((is_constructible< tuple<int>, vector<int> >(false)));
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BOOST_TEST((is_constructible<tuple<int>, int, int>(false)));
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BOOST_TEST((is_constructible< tuple<int, int> >(true)));
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BOOST_TEST((is_constructible<tuple<int, int>, int, int>(true)));
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BOOST_TEST((
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is_constructible<tuple<convertible, convertible>, int, int>(true)
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));
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BOOST_TEST((is_constructible<tuple<int, not_convertible>, int, int>(false)));
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BOOST_TEST((is_constructible<tuple<not_convertible, int>, int, int>(false)));
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BOOST_TEST((
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is_constructible<tuple<not_convertible, not_convertible>, int, int>(false)
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));
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#if defined(BOOST_FUSION_HAS_VARIADIC_VECTOR)
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// C++03 fusion::tuple has constructors that can never be used
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BOOST_TEST((is_constructible<tuple<int, int>, int>(false)));
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#endif
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BOOST_TEST((is_constructible<tuple<int, int>, int, int, int>(false)));
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#endif // FUSION_TEST_HAS_CONSTRUCTIBLE
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return boost::report_errors();
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}
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