proxy_reference.hpp

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// SPDX-License-Identifier: BSL-1.0
// SPDX-FileCopyrightText: Copyright (C) 2023 Tobias Hienzsch
 
#ifndef TETL_LINALG_PROXY_REFERENCE_HPP
#define TETL_LINALG_PROXY_REFERENCE_HPP
 
#include <etl/_linalg/concepts.hpp>
#include <etl/_type_traits/is_base_of.hpp>
 
namespace etl::linalg::detail {
 
struct proxy_reference_base { };
 
template <typename Reference, typename Value, typename Derived>
struct proxy_reference : proxy_reference_base {
    using reference_type = Reference;
    using value_type     = Value;
    using derived_type   = Derived;
 
    constexpr explicit proxy_reference(Reference reference) // NOLINT(bugprone-crtp-constructor-accessibility)
        : _reference(reference)
    {
    }
 
    constexpr operator value_type() const // NOLINT(readability-const-return-type)
    {
        return static_cast<value_type>(static_cast<Derived const&>(*this).to_value(_reference));
    }
 
    friend constexpr auto operator-(derived_type const& cs)
    {
        return -value_type(cs);
    }
 
    template <typename Rhs>
        requires(is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator+(derived_type lhs, Rhs rhs)
    {
        using rhs_value_type = typename Rhs::value_type;
        return value_type(lhs) + rhs_value_type(rhs);
    }
 
    template <typename Rhs>
        requires(not is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator+(derived_type lhs, Rhs rhs)
    {
        return value_type(lhs) + rhs;
    }
 
    template <typename Lhs>
        requires(not is_base_of_v<proxy_reference_base, Lhs>)
    friend constexpr auto operator+(Lhs lhs, derived_type rhs)
    {
        return lhs + value_type(rhs);
    }
 
    template <typename Rhs>
        requires(is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator-(derived_type lhs, Rhs rhs)
    {
        using rhs_value_type = typename Rhs::value_type;
        return value_type(lhs) - rhs_value_type(rhs);
    }
 
    template <typename Rhs>
        requires(not is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator-(derived_type lhs, Rhs rhs)
    {
        return value_type(lhs) - rhs;
    }
 
    template <typename Lhs>
        requires(not is_base_of_v<proxy_reference_base, Lhs>)
    friend constexpr auto operator-(Lhs lhs, derived_type rhs)
    {
        return lhs - value_type(rhs);
    }
 
    template <typename Rhs>
        requires(is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator*(derived_type lhs, Rhs rhs)
    {
        using rhs_value_type = typename Rhs::value_type;
        return value_type(lhs) * rhs_value_type(rhs);
    }
 
    template <typename Rhs>
        requires(not is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator*(derived_type lhs, Rhs rhs)
    {
        return value_type(lhs) * rhs;
    }
 
    template <typename Lhs>
        requires(not is_base_of_v<proxy_reference_base, Lhs>)
    friend constexpr auto operator*(Lhs lhs, derived_type rhs)
    {
        return lhs * value_type(rhs);
    }
 
    template <typename Rhs>
        requires(is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator/(derived_type lhs, Rhs rhs)
    {
        using rhs_value_type = typename Rhs::value_type;
        return value_type(lhs) / rhs_value_type(rhs);
    }
 
    template <typename Rhs>
        requires(not is_base_of_v<proxy_reference_base, Rhs>)
    friend constexpr auto operator/(derived_type lhs, Rhs rhs)
    {
        return value_type(lhs) / rhs;
    }
 
    template <typename Lhs>
        requires(not is_base_of_v<proxy_reference_base, Lhs>)
    friend constexpr auto operator/(Lhs lhs, derived_type rhs)
    {
        return lhs / value_type(rhs);
    }
 
    friend constexpr auto abs(derived_type const& x)
    {
        return abs_if_needed(value_type(static_cast<this_type const&>(x)));
    }
 
    friend constexpr auto real(derived_type const& x)
    {
        return real_if_needed(value_type(static_cast<this_type const&>(x)));
    }
 
    friend constexpr auto imag(derived_type const& x)
    {
        return imag_if_needed(value_type(static_cast<this_type const&>(x)));
    }
 
    friend constexpr auto conj(derived_type const& x)
    {
        return conj_if_needed(value_type(static_cast<this_type const&>(x)));
    }
 
private:
    using this_type = proxy_reference<Reference, Value, Derived>;
    Reference _reference; // NOLINT(cppcoreguidelines-avoid-const-or-ref-data-members)
};
 
} // namespace etl::linalg::detail
 
#endif // TETL_LINALG_PROXY_REFERENCE_HPP