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- // Copyright Louis Dionne 2013-2017
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
- #ifndef BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
- #define BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
- #include <boost/hana/equal.hpp>
- #include <boost/hana/eval_if.hpp>
- #include <boost/hana/front.hpp>
- #include <boost/hana/functional/always.hpp>
- #include <boost/hana/functional/fix.hpp>
- #include <boost/hana/functional/flip.hpp>
- #include <boost/hana/functional/on.hpp>
- #include <boost/hana/functional/partial.hpp>
- #include <boost/hana/integral_constant.hpp>
- #include <boost/hana/plus.hpp>
- #include <boost/hana/power.hpp>
- #include <boost/hana/range.hpp>
- #include <boost/hana/remove_at.hpp>
- #include <boost/hana/transform.hpp>
- #include <boost/hana/tuple.hpp>
- #include <boost/hana/unpack.hpp>
- #include <utility>
- #include "matrix.hpp"
- namespace cppcon {
- namespace hana = boost::hana;
- auto det = hana::fix([](auto det, auto&& m) -> decltype(auto) {
- auto matrix_minor = [=](auto&& m, auto i, auto j) -> decltype(auto) {
- return det(hana::unpack(
- hana::transform(
- hana::remove_at(rows(std::forward<decltype(m)>(m)), i),
- hana::partial(hana::flip(hana::remove_at), j)
- ),
- matrix
- ));
- };
- auto cofactor = [=](auto&& m, auto i, auto j) {
- return hana::power(hana::int_c<-1>, hana::plus(i, j)) *
- matrix_minor(std::forward<decltype(m)>(m), i, j);
- };
- return hana::eval_if(m.size() == hana::size_c<1>,
- hana::always(m.at(hana::size_c<0>, hana::size_c<0>)),
- [=](auto _) {
- auto cofactors_1st_row = hana::unpack(_(hana::make_range)(hana::size_c<0>, m.ncolumns()),
- hana::on(hana::make_tuple, hana::partial(cofactor, m, hana::size_c<0>))
- );
- return detail::tuple_scalar_product(hana::front(rows(m)), cofactors_1st_row);
- }
- );
- });
- } // end namespace cppcon
- #endif // !BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
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