extract_diagonal.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_EXTRACT_DIAGONAL_H
#define pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_EXTRACT_DIAGONAL_H
 
#include <prc/core/basic/functions/is_even.hpp>
#include <prc/core/functors/extract_diagonal.hpp>
#include <prc/core/functors/min.hpp>
#include <prc/core/functors/view.hpp>
#include <prc/core/tensor/operator/views/extract_diagonal.hpp>
 
namespace pRC
{
    template<class X, IsTensorish R = RemoveReference<X>>
        requires(isEven(R::Dimension))
    static inline constexpr auto extractDiagonal(X &&a)
    {
        if constexpr(IsInvocable<View, X>)
        {
            using V = RemoveReference<decltype(view(forward<X>(a)))>;
            return TensorViews::ExtractDiagonal<typename R::Type,
                decltype(pick<Min>(cut<2, 0>(typename R::Sizes()),
                    cut<2, 1>(typename R::Sizes()))),
                V>(view(forward<X>(a)));
        }
        else
        {
            return eval(extractDiagonal(a));
        }
    }
}
#endif // pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_EXTRACT_DIAGONAL_H