tensor_product.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_VIEWS_TENSOR_PRODUCT_H
#define pRC_CORE_TENSOR_VIEWS_TENSOR_PRODUCT_H
 
#include <prc/core/basic/sequence.hpp>
#include <prc/core/tensor/declarations.hpp>
 
namespace pRC::TensorViews
{
    template<class T, class N, class VA, class VB>
        requires IsTensorView<VA> && IsTensorView<VB>
    class TensorProduct : public View<T, N, TensorProduct<T, N, VA, VB>>
    {
    private:
        using Base = View<T, N, TensorProduct>;
 
    public:
        template<class XA, class XB>
            requires IsSame<VA, RemoveReference<XA>> &&
                         IsSame<VB, RemoveReference<XB>>
        TensorProduct(XA &&a, XB &&b)
            : mA(forward<XA>(a))
            , mB(forward<XB>(b))
        {
        }
 
        template<IsConvertible<Index>... Is>
            requires(sizeof...(Is) == Base::Dimension)
        constexpr decltype(auto) operator()(Is const... indices)
        {
            return this->call(indices...);
        }
 
        template<IsConvertible<Index>... Is>
            requires(sizeof...(Is) == Base::Dimension)
        constexpr decltype(auto) operator()(Is const... indices) const
        {
            return this->call(indices...);
        }
 
        constexpr decltype(auto) operator()(
            typename Base::Subscripts const &subscripts)
        {
            return expand(makeSeries<Index, VA::Dimension>(),
                       [this, &subscripts](auto const... seq) -> decltype(auto)
                       {
                           return mA(subscripts[seq]...);
                       }) *
                expand(makeRange<Index, VA::Dimension, Base::Dimension>(),
                    [this, &subscripts](auto const... seq) -> decltype(auto)
                    {
                        return mB(subscripts[seq]...);
                    });
        }
 
        constexpr decltype(auto) operator()(
            typename Base::Subscripts const &subscripts) const
        {
            return expand(makeSeries<Index, VA::Dimension>(),
                       [this, &subscripts](auto const... seq) -> decltype(auto)
                       {
                           return mA(subscripts[seq]...);
                       }) *
                expand(makeRange<Index, VA::Dimension, Base::Dimension>(),
                    [this, &subscripts](auto const... seq) -> decltype(auto)
                    {
                        return mB(subscripts[seq]...);
                    });
        }
 
        constexpr decltype(auto) operator[](Index const index) = delete;
        constexpr decltype(auto) operator[](Index const index) const = delete;
 
    private:
        VA mA;
        VB mB;
    };
}
#endif // pRC_CORE_TENSOR_VIEWS_TENSOR_PRODUCT_H