from_diagonal.hpp

Go to the documentation of this file.

// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_FROM_DIAGONAL_H
#define pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_FROM_DIAGONAL_H
 
#include <prc/core/basic/functions/is_even.hpp>
#include <prc/core/functors/view.hpp>
#include <prc/core/tensor/operator/views/from_diagonal.hpp>
 
namespace pRC
{
    template<Size... Ds, class X, IsTensorish R = RemoveReference<X>>
        requires(isEven(sizeof...(Ds))) &&
        (sizeof...(Ds) / 2 == R::Dimension) &&
        (cut<2, 0>(Sizes<Ds...>()) == typename R::Sizes() ||
            cut<2, 1>(Sizes<Ds...>()) == typename R::Sizes())
    static inline constexpr auto fromDiagonal(X &&a)
    {
        if constexpr(IsInvocable<View, X>)
        {
            using V = RemoveReference<decltype(view(forward<X>(a)))>;
            return TensorViews::FromDiagonal<typename R::Type, Sizes<Ds...>, V>(
                view(forward<X>(a)));
        }
        else
        {
            return eval(fromDiagonal<Ds...>(a));
        }
    }
 
    template<class X, IsTensorish R = RemoveReference<X>>
    static inline constexpr auto fromDiagonal(X &&a)
    {
        return expand(makeSeries<Index, R::Dimension>(),
            [&a](auto const... seq)
            {
                return fromDiagonal<R::size(seq)..., R::size(seq)...>(
                    forward<X>(a));
            });
    }
}
#endif // pRC_CORE_TENSOR_OPERATOR_FUNCTIONS_FROM_DIAGONAL_H