1// Copyright Louis Dionne 2013-2022
2// Distributed under the Boost Software License, Version 1.0.
3// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
4
5#ifndef BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
6#define BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
7
8#include <boost/hana/equal.hpp>
9#include <boost/hana/eval_if.hpp>
10#include <boost/hana/front.hpp>
11#include <boost/hana/functional/always.hpp>
12#include <boost/hana/functional/fix.hpp>
13#include <boost/hana/functional/flip.hpp>
14#include <boost/hana/functional/on.hpp>
15#include <boost/hana/functional/partial.hpp>
16#include <boost/hana/integral_constant.hpp>
17#include <boost/hana/plus.hpp>
18#include <boost/hana/power.hpp>
19#include <boost/hana/range.hpp>
20#include <boost/hana/remove_at.hpp>
21#include <boost/hana/transform.hpp>
22#include <boost/hana/tuple.hpp>
23#include <boost/hana/unpack.hpp>
24
25#include <utility>
26
27#include "matrix.hpp"
28
29
30namespace cppcon {
31 namespace hana = boost::hana;
32 auto det = hana::fix([](auto det, auto&& m) -> decltype(auto) {
33 auto matrix_minor = [=](auto&& m, auto i, auto j) -> decltype(auto) {
34 return det(hana::unpack(
35 hana::transform(
36 hana::remove_at(rows(std::forward<decltype(m)>(m)), i),
37 hana::partial(hana::flip(hana::remove_at), j)
38 ),
39 matrix
40 ));
41 };
42
43 auto cofactor = [=](auto&& m, auto i, auto j) {
44 return hana::power(hana::int_c<-1>, hana::plus(i, j)) *
45 matrix_minor(std::forward<decltype(m)>(m), i, j);
46 };
47
48 return hana::eval_if(m.size() == hana::size_c<1>,
49 hana::always(m.at(hana::size_c<0>, hana::size_c<0>)),
50 [=](auto _) {
51 auto cofactors_1st_row = hana::unpack(_(hana::make_range)(hana::size_c<0>, m.ncolumns()),
52 hana::on(hana::make_tuple, hana::partial(cofactor, m, hana::size_c<0>))
53 );
54 return detail::tuple_scalar_product(hana::front(rows(m)), cofactors_1st_row);
55 }
56 );
57 });
58} // end namespace cppcon
59
60#endif // !BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
61

source code of boost/libs/hana/example/cppcon_2014/matrix/det.hpp