hana/fwd/div.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::div`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_FWD_DIV_HPP
0011 #define BOOST_HANA_FWD_DIV_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/core/when.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     //! Generalized integer division.
0019     //! @ingroup group-EuclideanRing
0020     //!
0021     //!
0022     //! Cross-type version of the method
0023     //! --------------------------------
0024     //! The `div` method is "overloaded" to handle distinct data types
0025     //! with certain properties. Specifically, `div` is defined for
0026     //! _distinct_ data types `A` and `B` such that
0027     //! 1. `A` and `B` share a common data type `C`, as determined by the
0028     //!    `common` metafunction
0029     //! 2. `A`, `B` and `C` are all `EuclideanRing`s when taken individually
0030     //! 3. `to<C> : A -> B` and `to<C> : B -> C` are `Ring`-embeddings, as
0031     //!    determined by the `is_embedding` metafunction.
0032     //!
0033     //! In that case, the `div` method is defined as
0034     //! @code
0035     //!     div(x, y) = div(to<C>(x), to<C>(y))
0036     //! @endcode
0037     //!
0038     //!
0039     //! Example
0040     //! -------
0041     //! @include example/div.cpp
0042 #ifdef BOOST_HANA_DOXYGEN_INVOKED
0043     constexpr auto div = [](auto&& x, auto&& y) -> decltype(auto) {
0044         return tag-dispatched;
0045     };
0046 #else
0047     template <typename T, typename U, typename = void>
0048     struct div_impl : div_impl<T, U, when<true>> { };
0049
0050     struct div_t {
0051         template <typename X, typename Y>
0052         constexpr decltype(auto) operator()(X&& x, Y&& y) const;
0053     };
0054
0055     BOOST_HANA_INLINE_VARIABLE constexpr div_t div{};
0056 #endif
0057 }} // end namespace boost::hana
0058
0059 #endif // !BOOST_HANA_FWD_DIV_HPP