ceph/src/boost/libs/hana/include/boost/hana/fwd/power.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::power`.
   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_FWD_POWER_HPP
  11 #define BOOST_HANA_FWD_POWER_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Elevate a ring element to its `n`th power.
  19     //! @ingroup group-Ring
  20     //!
  21     //! Specifically, `power(x, n)`, is equivalent to multiplying `x` with
  22     //! itself `n` times using the Ring's multiplication. If the power is
  23     //! equal to `zero`, the Ring's identity (`one`) is returned.
  24     //!
  25     //! @param x
  26     //! A `Ring` element that is elevated to its `n`th power.
  27     //!
  28     //! @param n
  29     //! A non-negative `IntegralConstant` representing the power to which `x`
  30     //! is elevated.
  31     //!
  32     //!
  33     //! @note
  34     //! Only the tag of `x` is used for tag-dispatching.
  35     //!
  36     //! Example
  37     //! -------
  38     //! @include example/power.cpp
  39 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  40     constexpr auto power = [](auto&& x, auto const& n) -> decltype(auto) {
  41         return tag-dispatched;
  42     };
  43 #else
  44     template <typename R, typename = void>
  45     struct power_impl : power_impl<R, when<true>> { };
  46
  47     struct power_t {
  48         template <typename X, typename N>
  49         constexpr decltype(auto) operator()(X&& x, N const& n) const;
  50     };
  51
  52     constexpr power_t power{};
  53 #endif
  54 BOOST_HANA_NAMESPACE_END
  55
  56 #endif // !BOOST_HANA_FWD_POWER_HPP