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74 lines
2.4 KiB
C++
74 lines
2.4 KiB
C++
/*
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@copyright Louis Dionne 2015
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
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#define BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
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#include <boost/hana/constant.hpp>
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#include <boost/hana/foldable.hpp>
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#include <boost/hana/functional/always.hpp>
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#include <boost/hana/functional/compose.hpp>
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#include <boost/hana/functional/fix.hpp>
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#include <boost/hana/functional/on.hpp>
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#include <boost/hana/functional/partial.hpp>
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#include <boost/hana/functional/placeholder.hpp>
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#include <boost/hana/functor.hpp>
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#include <boost/hana/integral_constant.hpp>
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#include <boost/hana/iterable.hpp>
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#include <boost/hana/sequence.hpp>
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#include <boost/hana/logical.hpp>
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#include <boost/hana/monoid.hpp>
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#include <boost/hana/range.hpp>
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#include <boost/hana/ring.hpp>
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#include <boost/hana/tuple.hpp>
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#include <utility>
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#include "matrix.hpp"
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namespace cppcon {
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namespace detail {
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auto remove_at = [](auto n, auto xs) {
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using namespace boost::hana;
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using L = datatype_t<decltype(xs)>;
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auto with_indices = zip(xs, to<L>(range(size_t<0>, length(xs))));
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auto removed = filter(with_indices, compose(n != _, last));
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return transform(removed, head);
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};
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}
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auto det = boost::hana::fix([](auto det, auto&& m) -> decltype(auto) {
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using namespace boost::hana;
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auto matrix_minor = [=](auto&& m, auto i, auto j) -> decltype(auto) {
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return det(unpack(
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transform(
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detail::remove_at(i, rows(std::forward<decltype(m)>(m))),
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partial(detail::remove_at, j)
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),
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matrix
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));
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};
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auto cofactor = [=](auto&& m, auto i, auto j) {
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return power(int_<-1>, plus(i, j)) *
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matrix_minor(std::forward<decltype(m)>(m), i, j);
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};
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return eval_if(m.size() == size_t<1>,
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always(m.at(size_t<0>, size_t<0>)),
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[=](auto _) {
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auto cofactors_1st_row = unpack(_(range)(size_t<0>, m.ncolumns()),
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on(make<Tuple>, partial(cofactor, m, size_t<0>))
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);
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return detail::tuple_scalar_product(head(rows(m)), cofactors_1st_row);
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}
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);
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});
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} // end namespace cppcon
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#endif // !BOOST_HANA_EXAMPLE_CPPCON_2014_MATRIX_DET_HPP
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