cross_product.hpp

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// Copyright (c) 2020--present, The Simons Foundation
// This file is part of TRIQS/nda and is licensed under the Apache License, Version 2.0.
// SPDX-License-Identifier: Apache-2.0
// See LICENSE in the root of this distribution for details.

 
#pragma once
 
#include "../declarations.hpp"
#include "../macros.hpp"
#include "../traits.hpp"
 
namespace nda::linalg {

  template <typename V>
  auto cross_product(V const &x, V const &y) {
    EXPECTS_WITH_MESSAGE(x.shape()[0] == 3, "nda::linalg::cross_product: Only defined for 3-dimensional vectors");
    EXPECTS_WITH_MESSAGE(y.shape()[0] == 3, "nda::linalg::cross_product: Only defined for 3-dimensional vectors");
    array<get_value_t<V>, 1> r(3);
    r(0) = x(1) * y(2) - y(1) * x(2);
    r(1) = -x(0) * y(2) + y(0) * x(2);
    r(2) = x(0) * y(1) - y(0) * x(1);
    return r;
  }
 
} // namespace nda::linalg