ceph/src/boost/libs/hana/include/boost/hana/negate.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::negate`.
   4
   5 @copyright Louis Dionne 2013-2016
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_NEGATE_HPP
  11 #define BOOST_HANA_NEGATE_HPP
  12
  13 #include <boost/hana/fwd/negate.hpp>
  14
  15 #include <boost/hana/concept/group.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/dispatch.hpp>
  18 #include <boost/hana/fwd/minus.hpp>
  19 #include <boost/hana/zero.hpp>
  20
  21 #include <type_traits>
  22
  23
  24 BOOST_HANA_NAMESPACE_BEGIN
  25     //! @cond
  26     template <typename X>
  27     constexpr decltype(auto) negate_t::operator()(X&& x) const {
  28         using G = typename hana::tag_of<X>::type;
  29         using Negate = BOOST_HANA_DISPATCH_IF(negate_impl<G>,
  30             hana::Group<G>::value
  31         );
  32
  33     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  34         static_assert(hana::Group<G>::value,
  35         "hana::negate(x) requires 'x' to be in a Group");
  36     #endif
  37
  38         return Negate::apply(static_cast<X&&>(x));
  39     }
  40     //! @endcond
  41
  42     template <typename T, bool condition>
  43     struct negate_impl<T, when<condition>> : default_ {
  44         template <typename X>
  45         static constexpr decltype(auto) apply(X&& x)
  46         { return hana::minus(hana::zero<T>(), static_cast<X&&>(x)); }
  47     };
  48
  49     //////////////////////////////////////////////////////////////////////////
  50     // Model for arithmetic data types
  51     //////////////////////////////////////////////////////////////////////////
  52     template <typename T>
  53     struct negate_impl<T, when<std::is_arithmetic<T>::value &&
  54                                !std::is_same<bool, T>::value>> {
  55         template <typename X>
  56         static constexpr decltype(auto) apply(X&& x)
  57         { return -static_cast<X&&>(x); }
  58     };
  59 BOOST_HANA_NAMESPACE_END
  60
  61 #endif // !BOOST_HANA_NEGATE_HPP