dim.hpp

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#ifndef GKO_CORE_BASE_DIM_HPP_
#define GKO_CORE_BASE_DIM_HPP_


#include <ginkgo/core/base/types.hpp>
#include <ginkgo/core/base/utils.hpp>


namespace gko {


template <size_type Dimensionality, typename DimensionType = size_type>
struct dim {
    static constexpr size_type dimensionality = Dimensionality;

    using dimension_type = DimensionType;

    constexpr GKO_ATTRIBUTES dim(const dimension_type &size = dimension_type{})
        : first_{size}, rest_{size}
    {}

    template <typename... Rest>
    constexpr GKO_ATTRIBUTES dim(const dimension_type &first,
                                 const Rest &... rest)
        : first_{first}, rest_{static_cast<dimension_type>(rest)...}
    {}

    constexpr GKO_ATTRIBUTES const dimension_type &operator[](
        const size_type &dimension) const noexcept
    {
        return GKO_ASSERT(dimension < dimensionality), *(&first_ + dimension);
    }

    GKO_ATTRIBUTES dimension_type &operator[](
        const size_type &dimension) noexcept
    {
        return GKO_ASSERT(dimension < dimensionality), *(&first_ + dimension);
    }

    constexpr GKO_ATTRIBUTES operator bool() const
    {
        return static_cast<bool>(first_) && static_cast<bool>(rest_);
    }

    friend constexpr GKO_ATTRIBUTES bool operator==(const dim &x, const dim &y)
    {
        return x.first_ == y.first_ && x.rest_ == y.rest_;
    }

    friend constexpr GKO_ATTRIBUTES dim operator*(const dim &x, const dim &y)
    {
        return dim(x.first_ * y.first_, x.rest_ * y.rest_);
    }

private:
    constexpr GKO_ATTRIBUTES dim(const dimension_type first,
                                 dim<dimensionality - 1> rest)
        : first_{first}, rest_{rest}
    {}

    dimension_type first_;
    dim<dimensionality - 1, dimension_type> rest_;
};


// base case for dim recursive template
template <typename DimensionType>
struct dim<1u, DimensionType> {
    static constexpr size_type dimensionality = 1u;

    using dimension_type = DimensionType;

    constexpr GKO_ATTRIBUTES dim(const dimension_type &size = dimension_type{})
        : first_{size}
    {}

    constexpr GKO_ATTRIBUTES const dimension_type &operator[](
        const size_type &dimension) const noexcept
    {
        return *(&first_ + dimension);
    }

    GKO_ATTRIBUTES dimension_type &operator[](const size_type &dimension)
    {
        return *(&first_ + dimension);
    }

    constexpr GKO_ATTRIBUTES operator bool() const
    {
        return static_cast<bool>(first_);
    }

    friend constexpr GKO_ATTRIBUTES bool operator==(const dim &x, const dim &y)
    {
        return x.first_ == y.first_;
    }

    friend constexpr GKO_ATTRIBUTES dim operator*(const dim &x, const dim &y)
    {
        return dim(x.first_ * y.first_);
    }

private:
    dimension_type first_;
};


template <size_type Dimensionality, typename DimensionType>
constexpr GKO_ATTRIBUTES GKO_INLINE bool operator!=(
    const dim<Dimensionality, DimensionType> &x,
    const dim<Dimensionality, DimensionType> &y)
{
    return !(x == y);
}


template <typename DimensionType>
constexpr GKO_ATTRIBUTES GKO_INLINE dim<2, DimensionType> transpose(
    const dim<2, DimensionType> &dimensions) noexcept
{
    return {dimensions[1], dimensions[0]};
}


}  // namespace gko


#endif  // GKO_CORE_BASE_DIM_HPP_