direct_sum.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_VIEWS_DIRECT_SUM_H
#define pRC_CORE_TENSOR_VIEWS_DIRECT_SUM_H
 
#include <prc/core/basic/sequence.hpp>
#include <prc/core/tensor/type_traits.hpp>
#include <prc/core/value/functions/cast.hpp>
 
namespace pRC::TensorViews
{
    template<class T, class N, class VA, class VB>
    class DirectSum : public View<T, N, DirectSum<T, N, VA, VB>>
    {
        static_assert(IsTensorView<VA>());
        static_assert(IsTensorView<VB>());
 
    private:
        using Base = View<T, N, DirectSum>;
 
    public:
        template<class XA, class XB, If<IsSame<VA, RemoveReference<XA>>> = 0,
            If<IsSame<VB, RemoveReference<XB>>> = 0>
        DirectSum(XA &&a, XB &&b)
            : mA(forward<XA>(a))
            , mB(forward<XB>(b))
        {
        }
 
        template<class... Is, If<All<IsConvertible<Is, Index>...>> = 0,
            If<IsSatisfied<(sizeof...(Is) == typename Base::Dimension())>> = 0>
        constexpr decltype(auto) operator()(Is const... indices)
        {
            return expand(
                makeSeries<Index, typename Base::Dimension{}>(),
                [this](auto const &indices, auto const... seq) -> T
                {
                    if(((indices[seq] < VA::size(seq)) && ...))
                    {
                        return mA(indices[seq]...);
                    }
                    else if(((indices[seq] >= VA::size(seq)) && ...))
                    {
                        return mB((indices[seq] - VA::size(seq))...);
                    }
                    else
                    {
                        return zero();
                    }
                },
                Indices<sizeof...(Is)>(indices...));
        }
 
        template<class... Is, If<All<IsConvertible<Is, Index>...>> = 0,
            If<IsSatisfied<(sizeof...(Is) == typename Base::Dimension())>> = 0>
        constexpr decltype(auto) operator()(Is const... indices) const
        {
            return expand(
                makeSeries<Index, typename Base::Dimension{}>(),
                [this](auto const &indices, auto const... seq) -> T
                {
                    if(((indices[seq] < VA::size(seq)) && ...))
                    {
                        return mA(indices[seq]...);
                    }
                    else if(((indices[seq] >= VA::size(seq)) && ...))
                    {
                        return mB((indices[seq] - VA::size(seq))...);
                    }
                    else
                    {
                        return zero();
                    }
                },
                Indices<sizeof...(Is)>(indices...));
        }
 
        constexpr decltype(auto) operator()(
            typename Base::Subscripts const &subscripts)
        {
            return this->call(subscripts);
        }
 
        constexpr decltype(auto) operator()(
            typename Base::Subscripts const &subscripts) const
        {
            return this->call(subscripts);
        }
 
    private:
        VA mA;
        VB mB;
    };
}
#endif // pRC_CORE_TENSOR_VIEWS_DIRECT_SUM_H