52 lines
1.5 KiB
C++
52 lines
1.5 KiB
C++
/*!
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@file
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Forward declares `boost::hana::min`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_FWD_MIN_HPP
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#define BOOST_HANA_FWD_MIN_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! Returns the smallest of its arguments according to the `less` ordering.
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//! @ingroup group-Orderable
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//!
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//!
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//! @todo
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//! We can't specify the signature right now, because the tag of the
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//! returned object depends on whether `x < y` or not. If we wanted to be
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//! mathematically correct, we should probably ask that `if_(cond, x, y)`
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//! returns a common data type of `x` and `y`, and then the behavior
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//! of `min` would follow naturally. However, I'm unsure whether this
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//! is desirable because that's a big requirement.
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//!
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//!
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//! Example
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//! -------
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//! @include example/min.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto min = [](auto&& x, auto&& y) -> decltype(auto) {
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return tag-dispatched;
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};
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#else
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template <typename T, typename U, typename = void>
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struct min_impl : min_impl<T, U, when<true>> { };
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struct min_t {
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template <typename X, typename Y>
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constexpr decltype(auto) operator()(X&& x, Y&& y) const;
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};
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constexpr min_t min{};
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#endif
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_FWD_MIN_HPP
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