hana/fwd/mod.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::mod`.
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_MOD_HPP
0011 #define BOOST_HANA_FWD_MOD_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 modulus.
0019     //! @ingroup group-EuclideanRing
0020     //!
0021     //! Given two elements of an EuclideanRing `x` and `y`, with `y`
0022     //! nonzero, `mod` returns the modulus of the division of `x` by `y`.
0023     //! In other words, `mod` can be seen as an equivalent to `%`.
0024     //!
0025     //! Cross-type version of the method
0026     //! --------------------------------
0027     //! The `mod` method is "overloaded" to handle distinct data types
0028     //! with certain properties. Specifically, `mod` is defined for
0029     //! _distinct_ data types `A` and `B` such that
0030     //! 1. `A` and `B` share a common data type `C`, as determined by the
0031     //!    `common` metafunction
0032     //! 2. `A`, `B` and `C` are all `EuclideanRing`s when taken individually
0033     //! 3. `to<C> : A -> B` and `to<C> : B -> C` are `Ring`-embeddings, as
0034     //!    determined by the `is_embedding` metafunction.
0035     //!
0036     //! In that case, `mod` is defined as
0037     //! @code
0038     //!     mod(x, y) = mod(to<C>(x), to<C>(y))
0039     //! @endcode
0040     //!
0041     //!
0042     //! Example
0043     //! -------
0044     //! @include example/mod.cpp
0045 #ifdef BOOST_HANA_DOXYGEN_INVOKED
0046     constexpr auto mod = [](auto&& x, auto&& y) -> decltype(auto) {
0047         return tag-dispatched;
0048     };
0049 #else
0050     template <typename T, typename U, typename = void>
0051     struct mod_impl : mod_impl<T, U, when<true>> { };
0052
0053     struct mod_t {
0054         template <typename X, typename Y>
0055         constexpr decltype(auto) operator()(X&& x, Y&& y) const;
0056     };
0057
0058     BOOST_HANA_INLINE_VARIABLE constexpr mod_t mod{};
0059 #endif
0060 }} // end namespace boost::hana
0061
0062 #endif // !BOOST_HANA_FWD_MOD_HPP