boost/hana/fwd/less_equal.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::less_equal`.
   4
   5 @copyright Louis Dionne 2013-2017
   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_LESS_EQUAL_HPP
  11 #define BOOST_HANA_FWD_LESS_EQUAL_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15 #include <boost/hana/detail/nested_than_fwd.hpp>
  16
  17
  18 BOOST_HANA_NAMESPACE_BEGIN
  19     //! Returns a `Logical` representing whether `x` is less than or
  20     //! equal to `y`.
  21     //! @ingroup group-Orderable
  22     //!
  23     //!
  24     //! Signature
  25     //! ---------
  26     //! Given a Logical `Bool` and two Orderables `A` and `B` with a common
  27     //! embedding, the signature is
  28     //! @f$ \mathrm{less\_equal} : A \times B \to Bool @f$.
  29     //!
  30     //! @param x, y
  31     //! Two objects to compare.
  32     //!
  33     //!
  34     //! Example
  35     //! -------
  36     //! @include example/less_equal.cpp
  37 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  38     constexpr auto less_equal = [](auto&& x, auto&& y) {
  39         return tag-dispatched;
  40     };
  41 #else
  42     template <typename T, typename U, typename = void>
  43     struct less_equal_impl : less_equal_impl<T, U, when<true>> { };
  44
  45     struct less_equal_t : detail::nested_than<less_equal_t> {
  46         template <typename X, typename Y>
  47         constexpr auto operator()(X&& x, Y&& y) const;
  48     };
  49
  50     constexpr less_equal_t less_equal{};
  51 #endif
  52 BOOST_HANA_NAMESPACE_END
  53
  54 #endif // !BOOST_HANA_FWD_LESS_EQUAL_HPP