xexpression.hpp

/***************************************************************************
 * Copyright (c) Johan Mabille, Sylvain Corlay and Wolf Vollprecht          *
 * Copyright (c) QuantStack                                                 *
 *                                                                          *
 * Distributed under the terms of the BSD 3-Clause License.                 *
 *                                                                          *
 * The full license is in the file LICENSE, distributed with this software. *
 ****************************************************************************/
 
#ifndef XTENSOR_EXPRESSION_HPP
#define XTENSOR_EXPRESSION_HPP
 
#include <cstddef>
#include <type_traits>
#include <vector>
 
#include <xtl/xclosure.hpp>
#include <xtl/xmeta_utils.hpp>
#include <xtl/xtype_traits.hpp>
 
#include "../core/xlayout.hpp"
#include "../core/xshape.hpp"
#include "../core/xtensor_forward.hpp"
#include "../utils/xutils.hpp"
 
namespace xt
{
 
    /***************************
     * xexpression declaration *
     ***************************/

    template <class D>
    class xexpression
    {
    public:
 
        using derived_type = D;
 
        derived_type& derived_cast() & noexcept;
        const derived_type& derived_cast() const& noexcept;
        derived_type derived_cast() && noexcept;
 
    protected:
 
        xexpression() = default;
        ~xexpression() = default;
 
        xexpression(const xexpression&) = default;
        xexpression& operator=(const xexpression&) = default;
 
        xexpression(xexpression&&) = default;
        xexpression& operator=(xexpression&&) = default;
    };
 
    /************************************
     * xsharable_expression declaration *
     ************************************/
 
    template <class E>
    class xshared_expression;
 
    template <class E>
    class xsharable_expression;
 
    namespace detail
    {
        template <class E>
        xshared_expression<E> make_xshared_impl(xsharable_expression<E>&&);
    }
 
    template <class D>
    class xsharable_expression : public xexpression<D>
    {
    protected:
 
        xsharable_expression();
        ~xsharable_expression() = default;
 
        xsharable_expression(const xsharable_expression&) = default;
        xsharable_expression& operator=(const xsharable_expression&) = default;
 
        xsharable_expression(xsharable_expression&&) = default;
        xsharable_expression& operator=(xsharable_expression&&) = default;
 
    private:
 
        std::shared_ptr<D> p_shared;
 
        friend xshared_expression<D> detail::make_xshared_impl<D>(xsharable_expression<D>&&);
    };
 
    /******************************
     * xexpression implementation *
     ******************************/


    template <class D>
    inline auto xexpression<D>::derived_cast() & noexcept -> derived_type&
    {
        return *static_cast<derived_type*>(this);
    }

    template <class D>
    inline auto xexpression<D>::derived_cast() const& noexcept -> const derived_type&
    {
        return *static_cast<const derived_type*>(this);
    }

    template <class D>
    inline auto xexpression<D>::derived_cast() && noexcept -> derived_type
    {
        return *static_cast<derived_type*>(this);
    }

 
    /***************************************
     * xsharable_expression implementation *
     ***************************************/
 
    template <class D>
    inline xsharable_expression<D>::xsharable_expression()
        : p_shared(nullptr)
    {
    }

 
    namespace detail
    {
        template <template <class> class B, class E>
        struct is_crtp_base_of_impl : std::is_base_of<B<E>, E>
        {
        };
 
        template <template <class> class B, class E, template <class> class F>
        struct is_crtp_base_of_impl<B, F<E>>
            : std::disjunction<std::is_base_of<B<E>, F<E>>, std::is_base_of<B<F<E>>, F<E>>>
        {
        };
    }
 
    template <template <class> class B, class E>
    using is_crtp_base_of = detail::is_crtp_base_of_impl<B, std::decay_t<E>>;
 
    template <class E>
    using is_xexpression = is_crtp_base_of<xexpression, E>;
 
    template <class E>
    concept xexpression_concept = is_xexpression<E>::value;
 
    template <class E, class R = void>
    using enable_xexpression = typename std::enable_if<is_xexpression<E>::value, R>::type;
 
    template <class E, class R = void>
    using disable_xexpression = typename std::enable_if<!is_xexpression<E>::value, R>::type;
 
    template <class... E>
    using has_xexpression = std::disjunction<is_xexpression<E>...>;
 
    template <class E>
    using is_xsharable_expression = is_crtp_base_of<xsharable_expression, E>;
 
    template <class E, class R = void>
    using enable_xsharable_expression = typename std::enable_if<is_xsharable_expression<E>::value, R>::type;
 
    template <class E, class R = void>
    using disable_xsharable_expression = typename std::enable_if<!is_xsharable_expression<E>::value, R>::type;
 
    template <class LHS, class RHS>
    struct can_assign : std::is_assignable<LHS, RHS>
    {
    };
 
    template <class LHS, class RHS, class R = void>
    using enable_assignable_expression = typename std::enable_if<can_assign<LHS, RHS>::value, R>::type;
 
    template <class LHS, class RHS, class R = void>
    using enable_not_assignable_expression = typename std::enable_if<!can_assign<LHS, RHS>::value, R>::type;
 
    /***********************
     * evaluation_strategy *
     ***********************/
 
    namespace detail
    {
        struct option_base
        {
        };
    }
 
    namespace evaluation_strategy
    {
 
        struct immediate_type : xt::detail::option_base
        {
        };
 
        constexpr auto immediate = std::tuple<immediate_type>{};
 
        struct lazy_type : xt::detail::option_base
        {
        };
 
        constexpr auto lazy = std::tuple<lazy_type>{};
 
        /*
        struct cached {};
        */
    }
 
    template <class T>
    struct is_evaluation_strategy : std::is_base_of<detail::option_base, std::decay_t<T>>
    {
    };
 
    /************
     * xclosure *
     ************/
 
    template <class T>
    class xscalar;
 
    template <class E, class EN = void>
    struct xclosure
    {
        using type = xtl::closure_type_t<E>;
    };
 
    template <class E>
    struct xclosure<xshared_expression<E>, std::enable_if_t<true>>
    {
        using type = xshared_expression<E>;  // force copy
    };
 
    template <class E>
    struct xclosure<E, disable_xexpression<std::decay_t<E>>>
    {
        using type = xscalar<xtl::closure_type_t<E>>;
    };
 
    template <class E>
    using xclosure_t = typename xclosure<E>::type;
 
    template <class E, class EN = void>
    struct const_xclosure
    {
        using type = xtl::const_closure_type_t<E>;
    };
 
    template <class E>
    struct const_xclosure<E, disable_xexpression<std::decay_t<E>>>
    {
        using type = xscalar<xtl::const_closure_type_t<E>>;
    };
 
    template <class E>
    struct const_xclosure<xshared_expression<E>&, std::enable_if_t<true>>
    {
        using type = xshared_expression<E>;  // force copy
    };
 
    template <class E>
    using const_xclosure_t = typename const_xclosure<E>::type;
 
    /*************************
     * expression tag system *
     *************************/
 
    struct xtensor_expression_tag
    {
    };
 
    struct xoptional_expression_tag
    {
    };
 
    namespace extension
    {
        template <class E, class = void_t<int>>
        struct get_expression_tag_impl
        {
            using type = xtensor_expression_tag;
        };
 
        template <class E>
        struct get_expression_tag_impl<E, void_t<typename std::decay_t<E>::expression_tag>>
        {
            using type = typename std::decay_t<E>::expression_tag;
        };
 
        template <class E>
        struct get_expression_tag : get_expression_tag_impl<E>
        {
        };
 
        template <class E>
        using get_expression_tag_t = typename get_expression_tag<E>::type;
 
        template <class... T>
        struct expression_tag_and;
 
        template <>
        struct expression_tag_and<>
        {
            using type = xtensor_expression_tag;
        };
 
        template <class T>
        struct expression_tag_and<T>
        {
            using type = T;
        };
 
        template <class T>
        struct expression_tag_and<T, T>
        {
            using type = T;
        };
 
        template <class T>
        struct expression_tag_and<xtensor_expression_tag, T>
        {
            using type = T;
        };
 
        template <class T>
        struct expression_tag_and<T, xtensor_expression_tag> : expression_tag_and<xtensor_expression_tag, T>
        {
        };
 
        template <>
        struct expression_tag_and<xtensor_expression_tag, xtensor_expression_tag>
        {
            using type = xtensor_expression_tag;
        };
 
        template <class T1, class... T>
        struct expression_tag_and<T1, T...> : expression_tag_and<T1, typename expression_tag_and<T...>::type>
        {
        };
 
        template <class... T>
        using expression_tag_and_t = typename expression_tag_and<T...>::type;
 
        struct xtensor_empty_base
        {
            using expression_tag = xtensor_expression_tag;
        };
    }
 
    template <class... T>
    struct xexpression_tag
    {
        using type = extension::expression_tag_and_t<
            extension::get_expression_tag_t<std::decay_t<const_xclosure_t<T>>>...>;
    };
 
    template <class... T>
    using xexpression_tag_t = typename xexpression_tag<T...>::type;
 
    template <class E>
    struct is_xtensor_expression : std::is_same<xexpression_tag_t<E>, xtensor_expression_tag>
    {
    };
 
    template <class E>
    struct is_xoptional_expression : std::is_same<xexpression_tag_t<E>, xoptional_expression_tag>
    {
    };
 
    /********************************
     * xoptional_comparable concept *
     ********************************/
 
    template <class... E>
    struct xoptional_comparable
        : std::conjunction<std::disjunction<is_xtensor_expression<E>, is_xoptional_expression<E>>...>
    {
    };
 
#define XTENSOR_FORWARD_CONST_METHOD(name)                                   \
    auto name() const -> decltype(std::declval<xtl::constify_t<E>>().name()) \
    {                                                                        \
        return m_ptr->name();                                                \
    }
 
#define XTENSOR_FORWARD_METHOD(name)                  \
    auto name() -> decltype(std::declval<E>().name()) \
    {                                                 \
        return m_ptr->name();                         \
    }
 
#define XTENSOR_FORWARD_CONST_ITERATOR_METHOD(name)                                               \
    template <layout_type L = XTENSOR_DEFAULT_TRAVERSAL>                                          \
    auto name() const noexcept -> decltype(std::declval<xtl::constify_t<E>>().template name<L>()) \
    {                                                                                             \
        return m_ptr->template name<L>();                                                         \
    }                                                                                             \
    template <layout_type L = XTENSOR_DEFAULT_TRAVERSAL, class S>                                 \
    auto name(const S& shape) const noexcept                                                      \
        -> decltype(std::declval<xtl::constify_t<E>>().template name<L>(shape))                   \
    {                                                                                             \
        return m_ptr->template name<L>();                                                         \
    }
 
#define XTENSOR_FORWARD_ITERATOR_METHOD(name)                                                 \
    template <layout_type L = XTENSOR_DEFAULT_TRAVERSAL, class S>                             \
    auto name(const S& shape) noexcept -> decltype(std::declval<E>().template name<L>(shape)) \
    {                                                                                         \
        return m_ptr->template name<L>();                                                     \
    }                                                                                         \
    template <layout_type L = XTENSOR_DEFAULT_TRAVERSAL>                                      \
    auto name() noexcept -> decltype(std::declval<E>().template name<L>())                    \
    {                                                                                         \
        return m_ptr->template name<L>();                                                     \
    }
 
    namespace detail
    {
        template <class E>
        struct expr_strides_type
        {
            using type = typename E::strides_type;
        };
 
        template <class E>
        struct expr_inner_strides_type
        {
            using type = typename E::inner_strides_type;
        };
 
        template <class E>
        struct expr_backstrides_type
        {
            using type = typename E::backstrides_type;
        };
 
        template <class E>
        struct expr_inner_backstrides_type
        {
            using type = typename E::inner_backstrides_type;
        };
 
        template <class E>
        struct expr_storage_type
        {
            using type = typename E::storage_type;
        };
    }

    template <class E>
    class xshared_expression : public xexpression<xshared_expression<E>>
    {
    public:
 
        using base_class = xexpression<xshared_expression<E>>;
 
        using value_type = typename E::value_type;
        using reference = typename E::reference;
        using const_reference = typename E::const_reference;
        using pointer = typename E::pointer;
        using const_pointer = typename E::const_pointer;
        using size_type = typename E::size_type;
        using difference_type = typename E::difference_type;
 
        using inner_shape_type = typename E::inner_shape_type;
        using shape_type = typename E::shape_type;
 
        using strides_type = xtl::mpl::
            eval_if_t<has_strides<E>, detail::expr_strides_type<E>, get_strides_type<shape_type>>;
        using backstrides_type = xtl::mpl::
            eval_if_t<has_strides<E>, detail::expr_backstrides_type<E>, get_strides_type<shape_type>>;
        using inner_strides_type = xtl::mpl::
            eval_if_t<has_strides<E>, detail::expr_inner_strides_type<E>, get_strides_type<shape_type>>;
        using inner_backstrides_type = xtl::mpl::
            eval_if_t<has_strides<E>, detail::expr_inner_backstrides_type<E>, get_strides_type<shape_type>>;
        using storage_type = xtl::mpl::eval_if_t<has_storage_type<E>, detail::expr_storage_type<E>, make_invalid_type<>>;
 
        using stepper = typename E::stepper;
        using const_stepper = typename E::const_stepper;
 
        using linear_iterator = typename E::linear_iterator;
        using const_linear_iterator = typename E::const_linear_iterator;
 
        using bool_load_type = typename E::bool_load_type;
 
        static constexpr layout_type static_layout = E::static_layout;
        static constexpr bool contiguous_layout = static_layout != layout_type::dynamic;
 
        explicit xshared_expression(const std::shared_ptr<E>& ptr);
        long use_count() const noexcept;
 
        template <class... Args>
        auto operator()(Args... args) -> decltype(std::declval<E>()(args...))
        {
            return m_ptr->operator()(args...);
        }
 
        XTENSOR_FORWARD_CONST_METHOD(shape)
        XTENSOR_FORWARD_CONST_METHOD(dimension)
        XTENSOR_FORWARD_CONST_METHOD(size)
        XTENSOR_FORWARD_CONST_METHOD(layout)
        XTENSOR_FORWARD_CONST_METHOD(is_contiguous)
 
        XTENSOR_FORWARD_ITERATOR_METHOD(begin)
        XTENSOR_FORWARD_ITERATOR_METHOD(end)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(begin)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(end)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(cbegin)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(cend)
 
        XTENSOR_FORWARD_ITERATOR_METHOD(rbegin)
        XTENSOR_FORWARD_ITERATOR_METHOD(rend)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(rbegin)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(rend)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(crbegin)
        XTENSOR_FORWARD_CONST_ITERATOR_METHOD(crend)
 
        XTENSOR_FORWARD_METHOD(linear_begin)
        XTENSOR_FORWARD_METHOD(linear_end)
        XTENSOR_FORWARD_CONST_METHOD(linear_begin)
        XTENSOR_FORWARD_CONST_METHOD(linear_end)
        XTENSOR_FORWARD_CONST_METHOD(linear_cbegin)
        XTENSOR_FORWARD_CONST_METHOD(linear_cend)
 
        XTENSOR_FORWARD_METHOD(linear_rbegin)
        XTENSOR_FORWARD_METHOD(linear_rend)
        XTENSOR_FORWARD_CONST_METHOD(linear_rbegin)
        XTENSOR_FORWARD_CONST_METHOD(linear_rend)
        XTENSOR_FORWARD_CONST_METHOD(linear_crbegin)
        XTENSOR_FORWARD_CONST_METHOD(linear_crend)
 
        template <class T = E>
        std::enable_if_t<has_strides<T>::value, const inner_strides_type&> strides() const
        {
            return m_ptr->strides();
        }
 
        template <class T = E>
        std::enable_if_t<has_strides<T>::value, const inner_strides_type&> backstrides() const
        {
            return m_ptr->backstrides();
        }
 
        template <class T = E>
        std::enable_if_t<has_data_interface<T>::value, pointer> data() noexcept
        {
            return m_ptr->data();
        }
 
        template <class T = E>
        std::enable_if_t<has_data_interface<T>::value, pointer> data() const noexcept
        {
            return m_ptr->data();
        }
 
        template <class T = E>
        std::enable_if_t<has_data_interface<T>::value, size_type> data_offset() const noexcept
        {
            return m_ptr->data_offset();
        }
 
        template <class T = E>
        std::enable_if_t<has_data_interface<T>::value, typename T::storage_type&> storage() noexcept
        {
            return m_ptr->storage();
        }
 
        template <class T = E>
        std::enable_if_t<has_data_interface<T>::value, const typename T::storage_type&> storage() const noexcept
        {
            return m_ptr->storage();
        }
 
        template <class It>
        reference element(It first, It last)
        {
            return m_ptr->element(first, last);
        }
 
        template <class It>
        const_reference element(It first, It last) const
        {
            return m_ptr->element(first, last);
        }
 
        template <class S>
        bool broadcast_shape(S& shape, bool reuse_cache = false) const
        {
            return m_ptr->broadcast_shape(shape, reuse_cache);
        }
 
        template <class S>
        bool has_linear_assign(const S& strides) const noexcept
        {
            return m_ptr->has_linear_assign(strides);
        }
 
        template <class S>
        auto stepper_begin(const S& shape) noexcept -> decltype(std::declval<E>().stepper_begin(shape))
        {
            return m_ptr->stepper_begin(shape);
        }
 
        template <class S>
        auto stepper_end(const S& shape, layout_type l) noexcept
            -> decltype(std::declval<E>().stepper_end(shape, l))
        {
            return m_ptr->stepper_end(shape, l);
        }
 
        template <class S>
        auto stepper_begin(const S& shape) const noexcept
            -> decltype(std::declval<const E>().stepper_begin(shape))
        {
            return static_cast<const E*>(m_ptr.get())->stepper_begin(shape);
        }
 
        template <class S>
        auto stepper_end(const S& shape, layout_type l) const noexcept
            -> decltype(std::declval<const E>().stepper_end(shape, l))
        {
            return static_cast<const E*>(m_ptr.get())->stepper_end(shape, l);
        }
 
    private:
 
        std::shared_ptr<E> m_ptr;
    };

    template <class E>
    inline xshared_expression<E>::xshared_expression(const std::shared_ptr<E>& ptr)
        : m_ptr(ptr)
    {
    }

    template <class E>
    inline long xshared_expression<E>::use_count() const noexcept
    {
        return m_ptr.use_count();
    }
 
    namespace detail
    {
        template <class E>
        inline xshared_expression<E> make_xshared_impl(xsharable_expression<E>&& expr)
        {
            if (expr.p_shared == nullptr)
            {
                expr.p_shared = std::make_shared<E>(std::move(expr).derived_cast());
            }
            return xshared_expression<E>(expr.p_shared);
        }
    }

    template <class E>
    inline xshared_expression<E> make_xshared(xexpression<E>&& expr)
    {
        static_assert(
            is_xsharable_expression<E>::value,
            "make_shared requires E to inherit from xsharable_expression"
        );
        return detail::make_xshared_impl(std::move(expr.derived_cast()));
    }

    template <class E>
    inline auto share(xexpression<E>& expr)
    {
        return make_xshared(std::move(expr));
    }

    template <class E>
    inline auto share(xexpression<E>&& expr)
    {
        return make_xshared(std::move(expr));
    }
 
#undef XTENSOR_FORWARD_METHOD
 
}
 
#endif