contract.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_TENSOR_VIEWS_CONTRACT_H
#define pRC_CORE_TENSOR_VIEWS_CONTRACT_H
 
#include <prc/core/basic/range.hpp>
#include <prc/core/basic/sequence.hpp>
#include <prc/core/tensor/declarations.hpp>
 
namespace pRC::TensorViews
{
    template<class T, class N, class S1, class S2, class V>
    class Contract;
 
    template<class T, class N, Index... ILs, Index... IRs, class V>
        requires IsTensorView<V> && ((V::size(ILs) == V::size(IRs)) && ...)
    class Contract<T, N, Sequence<Index, ILs...>, Sequence<Index, IRs...>, V>
        : public View<T, N,
              Contract<T, N, Sequence<Index, ILs...>, Sequence<Index, IRs...>,
                  V>>
    {
    private:
        using Base = View<T, N, Contract>;
 
    public:
        template<class X>
            requires IsSame<V, RemoveReference<X>>
        Contract(X &&a)
            : mA(forward<X>(a))
        {
        }
 
        template<IsConvertible<Index>... Is>
            requires(sizeof...(Is) == Base::Dimension)
        constexpr decltype(auto) operator()(Is const... indices)
        {
            auto c = Add::template Identity<T>();
 
            range<Sizes<V::size(ILs)...>>(
                [this, &c, indices...](auto const... loop)
                {
                    c += chip<ILs..., IRs...>(mA, loop..., loop...)(indices...);
                });
 
            return c;
        }
 
        template<IsConvertible<Index>... Is>
            requires(sizeof...(Is) == Base::Dimension)
        constexpr decltype(auto) operator()(Is const... indices) const
        {
            auto c = Add::template Identity<T>();
 
            range<Sizes<V::size(ILs)...>>(
                [this, &c, indices...](auto const... loop)
                {
                    c += chip<ILs..., IRs...>(mA, loop..., loop...)(indices...);
                });
 
            return c;
        }
 
        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);
        }
 
        constexpr decltype(auto) operator[](Index const index) = delete;
        constexpr decltype(auto) operator[](Index const index) const = delete;
 
    private:
        V mA;
    };
}
#endif // pRC_CORE_TENSOR_VIEWS_CONTRACT_H