Program Listing for File taxonomy.h¶

↰ Return to documentation for file (src/ifcgeom/taxonomy.h)

#ifndef TAXONOMY_H
#define TAXONOMY_H

#include "../ifcparse/express.h"
#include "../ifcparse/logger.h"

#include "conversion_settings.h"

#include <boost/variant.hpp>
#include <boost/functional/hash.hpp>
#include <boost/math/constants/constants.hpp>

#include <Eigen/Dense>

#include <map>
#include <string>
#include <tuple>
#include <exception>
#include <numeric>
#include <cstdint>
#include <cmath>
#include <array>
#include <limits>
#include <functional>
#include <algorithm>
#include <stdexcept>

#ifndef TAXONOMY_USE_UNIQUE_PTR
#ifndef TAXONOMY_USE_NAKED_PTR
#define TAXONOMY_USE_SHARED_PTR
#endif
#endif

#ifdef TAXONOMY_USE_SHARED_PTR
#include <memory>
#endif

// @todo don't do std::less but use hashing and cache hash values.

namespace boost { inline std::size_t hash_value(const boost::blank&) { return 0; } }

namespace ifcopenshell {

    namespace geom {

        namespace taxonomy {

#ifdef TAXONOMY_USE_SHARED_PTR
            template <typename T>
            T clone(T& t) {
                return t;
            }
            template <typename T, typename U>
            std::shared_ptr<T> cast(const std::shared_ptr<U>& u);
            template <typename T, typename U>
            std::shared_ptr<T> dcast(const std::shared_ptr<U>& u);
#endif
#ifdef TAXONOMY_USE_UNIQUE_PTR
            // untested currently
            template <typename T>
            T clone(T& t) {
                return t->clone_();
            }
            template <typename T, typename U>
            T* cast(const std::unique_ptr<U>& u);
            template <typename T, typename U>
            T* dcast(const std::unique_ptr<U>& u);
#endif
#ifdef TAXONOMY_USE_NAKED_PTR
            // untested currently
            template <typename T>
            T clone(T& t) {
                return t->clone_();
            }
            template <typename T, typename U>
            T* cast(const U*& u);
            template <typename T, typename U>
            T* dcast(const U*& u);
#endif

#ifdef TAXONOMY_USE_SHARED_PTR
#define DECLARE_PTR(item) \
typedef std::shared_ptr<item> ptr; \
typedef std::shared_ptr<const item> const_ptr;
#endif
#ifdef TAXONOMY_USE_UNIQUE_PTR
#define DECLARE_PTR(item) \
typedef std::uniqe_ptr<item> ptr; \
typedef std::uniqe_ptr<const item> ptr;
#endif
#ifdef TAXONOMY_USE_NAKED_PTR
#define DECLARE_PTR(item) \
typedef item* ptr; \
typedef item const* ptr;
#endif

#if defined(_MSC_VER)
#pragma warning(push)
#pragma warning(disable: 4275)
#endif

            class IFC_GEOM_API topology_error : public std::runtime_error {
            public:
                topology_error() : std::runtime_error("Generic topology error") {}
                topology_error(const char* const s) : std::runtime_error(s) {}
                ~topology_error() override;
            };

#if defined(_MSC_VER)
#pragma warning(pop)
#endif

            // Implementer note: If you add a new item type, be sure to do the following
            // 1) Add a new kind to this list
            // 2) Update the values array used by kind_to_string()
            // 3) Update the kinds_tuple with the class name of the new item
            // 4) Add compare function (see compare functions in taxonomy.cpp starting around line 9)
            // 4) Update Python bindings
            //    a) update list of assign_repr in IfcGeomWrapper.i
            //    b) update inheritance list in IfcGeomWrapper.i (around line 120 in the file)
            //    c) update item_to_pyobject function definition in type_conversion.i
            enum kinds {
                MATRIX4,
                POINT3,
                DIRECTION3,
                LINE,
                CIRCLE,
                ELLIPSE,
                BSPLINE_CURVE,
                OFFSET_CURVE,
                PLANE,
                CYLINDER,
                SPHERE,
                TORUS,
                BSPLINE_SURFACE,
                EDGE,
                LOOP,
                FACE,
                SHELL,
                SOLID,
                LOFT,
                EXTRUSION,
                REVOLVE,
                SWEEP_ALONG_CURVE,
                NODE,
                COLLECTION,
                BOOLEAN_RESULT,
                     FUNCTION_ITEM,
                FUNCTOR_ITEM,
                     PIECEWISE_FUNCTION,
                GRADIENT_FUNCTION,
                     CANT_FUNCTION,
                     OFFSET_FUNCTION,
                COLOUR,
                STYLE
            };

            IFC_GEOM_API const std::string& kind_to_string(kinds k);

            struct IFC_GEOM_API item {
            private:
                uint32_t identity_;
                static std::atomic_uint32_t counter_;
                mutable size_t computed_hash_;
            public:
                DECLARE_PTR(item)

                express::base instance;

                std::optional<bool> orientation;

                virtual item* clone_() const = 0;
                virtual kinds kind() const = 0;
                virtual void print(std::ostream&, int indent = 0) const;
                virtual void reverse() { throw taxonomy::topology_error(); }
                virtual size_t calc_hash() const = 0;
                virtual size_t hash() const {
                    if (computed_hash_) {
                        return computed_hash_;
                    }
                    computed_hash_ = calc_hash();
                    if (computed_hash_ == 0) {
                        computed_hash_++;
                    }
                    return computed_hash_;
                }

                item(const express::base& instance = express::base()) : identity_(counter_++), computed_hash_(0), instance(instance) {}

                virtual ~item() {}

                uint32_t identity() const { return identity_; }
            };

            namespace {

                template <typename T>
                const T& eigen_defaults();

                template <>
                const Eigen::Vector3d& eigen_defaults<Eigen::Vector3d>() {
                    static Eigen::Vector3d identity = Eigen::Vector3d::Zero();
                    return identity;
                }

                template <>
                const Eigen::Matrix4d& eigen_defaults<Eigen::Matrix4d>() {
                    static Eigen::Matrix4d identity = Eigen::Matrix4d::Identity();
                    return identity;
                }

            }

            template <typename T>
            struct IFC_GEOM_API eigen_base {
                T* components_;

                eigen_base() {
                    components_ = nullptr;
                }

                eigen_base(const eigen_base& other) {
                    this->components_ = other.components_ ? new T(*other.components_) : nullptr;
                }

                eigen_base(const T& other) {
                    this->components_ = new T(other);
                }

                eigen_base& operator=(const eigen_base& other) {
                    if (this != &other) {
                        this->components_ = other.components_ ? new T(*other.components_) : nullptr;
                    }
                    return *this;
                }

                void print_impl(std::ostream& o, const std::string& class_name, int indent = 0) const {
                    o << std::string(indent, ' ') << class_name;
                    if (this->components_) {
                        int n = T::RowsAtCompileTime * T::ColsAtCompileTime;
                        for (int i = 0; i < n; ++i) {
                            o << " " << (*components_)(i);
                        }
                    }
                    o << std::endl;
                }

                virtual ~eigen_base() {
                    delete this->components_;
                }

                const T& ccomponents() const {
                    if (this->components_) {
                        return *this->components_;
                    } else {
                        return eigen_defaults<T>();
                    }
                }

                T& components() {
                    if (!this->components_) {
                        this->components_ = new T(eigen_defaults<T>());
                    }
                    return *this->components_;
                }

                explicit operator bool() const {
                    return components_;
                }

                uint32_t hash_components() const {
                    size_t h = std::hash<size_t>{}(T::RowsAtCompileTime);
                    boost::hash_combine(h, std::hash<size_t>{}(T::ColsAtCompileTime));
                    if (components_) {
                        for (int i = 0; i < components_->size(); ++i) {
                            auto elem = *(components_->data() + (size_t)i);
                            boost::hash_combine(h, std::hash<typename T::Scalar>()(elem));
                        }
                    }
                    return (uint32_t)h;
                }
            };

            struct IFC_GEOM_API matrix4 : public item, public eigen_base<Eigen::Matrix4d> {
            private:
                void init(const Eigen::Vector3d& o, const Eigen::Vector3d& z, const Eigen::Vector3d& x) {
                    auto Z = z.normalized();
                    auto Y = Z.cross(x).normalized();
                    auto X = Y.cross(Z);
                    components_ = new Eigen::Matrix4d;
                    (*components_) <<
                        X(0), Y(0), Z(0), o(0),
                        X(1), Y(1), Z(1), o(1),
                        X(2), Y(2), Z(2), o(2),
                        0, 0, 0, 1.;
                    if (is_identity()) {
                        // @todo detect this earlier to save us the heapalloc.
                        delete components_;
                        components_ = nullptr;
                        tag = IDENTITY;
                    }
                }
            public:
                DECLARE_PTR(matrix4)

                enum tag_type {
                    IDENTITY, AFFINE_WO_SCALE, AFFINE_W_UNIFORM_SCALE, AFFINE_W_NONUNIFORM_SCALE, OTHER
                };
                tag_type tag;

                matrix4() : eigen_base(), tag(IDENTITY) {}
                matrix4(const Eigen::Matrix4d& c) : eigen_base(c), tag(OTHER) {}
                matrix4(const Eigen::Vector3d& o, const Eigen::Vector3d& z, const Eigen::Vector3d& x) : tag(AFFINE_WO_SCALE) {
                    init(o, z, x);
                }
                matrix4(const Eigen::Vector3d& o, const Eigen::Vector3d& z) : tag(AFFINE_WO_SCALE) {
                    auto x = Eigen::Vector3d(1, 0, 0);
                    auto y = z.cross(x);
                    if (y.squaredNorm() < 1.e-7) {
                        x = Eigen::Vector3d(0, 0, 1);
                    }
                    init(o, z, x);
                }

                bool is_identity() const {
                    return !components_ || components_->isIdentity();
                }

                void print(std::ostream& o, int indent = 0) const;

                virtual matrix4* clone_() const { return new matrix4(*this); }
                virtual kinds kind() const { return MATRIX4; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(MATRIX4), hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }

                void pre_multiply_scale(double s) {
                    components().block<3, 4>(0, 0) *= s;
                }

                void post_multiply_scale(double s) {
                    components().block<4, 3>(0, 0) *= s;
                }

                Eigen::Vector3d translation_part() const { return ccomponents().col(3).head<3>(); }
            };

            struct IFC_GEOM_API colour : public item, public eigen_base<Eigen::Vector3d> {
                DECLARE_PTR(colour)

                void print(std::ostream& o, int indent = 0) const;

                virtual colour* clone_() const { return new colour(*this); }
                virtual kinds kind() const { return COLOUR; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(COLOUR), hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }

                colour() : eigen_base() {}
                colour(double r, double g, double b) { components() << r, g, b; }

                const double& r() const { return ccomponents()[0]; }
                const double& g() const { return ccomponents()[1]; }
                const double& b() const { return ccomponents()[2]; }
            };

            struct IFC_GEOM_API style : public item {
                DECLARE_PTR(style)

                std::string name;
                colour diffuse;
                colour surface;
                colour specular;
                double specularity, transparency;
                bool use_surface_color;

                void print(std::ostream& o, int indent = 0) const;

                virtual style* clone_() const { return new style(*this); }
                virtual kinds kind() const { return STYLE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(STYLE), name, diffuse.hash(), surface.hash(), specular.hash(), specularity, transparency);
                    return boost::hash<decltype(v)>{}(v);
                }

                // @todo equality implementation based on values?
                bool operator==(const style& other) const { return instance == other.instance; }

                style() : specularity(std::numeric_limits<double>::quiet_NaN()), transparency(std::numeric_limits<double>::quiet_NaN()), use_surface_color(false) {}
                style(const std::string& name) : name(name), specularity(std::numeric_limits<double>::quiet_NaN()), transparency(std::numeric_limits<double>::quiet_NaN()), use_surface_color(false) {}

                const colour& get_color() const {
                    if (use_surface_color && surface) {
                        return surface;
                    }
                    return diffuse;
                }

                bool has_specularity() const {
                    return !std::isnan(specularity);
                }

                bool has_transparency() const {
                    return !std::isnan(transparency);
                }
            };

            struct IFC_GEOM_API geom_item : public item {
                DECLARE_PTR(geom_item)

                style::ptr surface_style;
                matrix4::ptr matrix;

                geom_item(const express::base& instance = express::base()) : item(instance), surface_style(nullptr) {}
                geom_item(const express::base instance, matrix4::ptr m) : item(instance), surface_style(nullptr), matrix(m) {}
                geom_item(matrix4::ptr m) : surface_style(nullptr), matrix(m) {}
            };

            struct IFC_GEOM_API implicit_item : public geom_item {
                DECLARE_PTR(implicit_item)
                using geom_item::geom_item;
            };

            struct IFC_GEOM_API function_item : public implicit_item {
                DECLARE_PTR(function_item)

                function_item(const express::base& instance = express::base()) : implicit_item(instance) {}
                function_item(function_item&&) = default;
                function_item(const function_item&) = default;

                virtual ~function_item() = default;
                virtual double start() const = 0;
                virtual double end() const = 0;
                virtual double length() const {
                    return end() - start();
                }

                virtual kinds kind() const { return FUNCTION_ITEM; }
                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(FUNCTION_ITEM), 0);
                    return boost::hash<decltype(v)>{}(v);
                };
            };

            struct IFC_GEOM_API functor_item : public function_item {
            DECLARE_PTR(functor_item)

            functor_item(double length, std::function<Eigen::Matrix4d(double u)> fn, const express::base& instance = express::base()) : function_item(instance),
                         length_(length), fn_(fn) {}
            functor_item(functor_item&&) = default;
            functor_item(const functor_item&) = default;
            virtual ~functor_item() = default;

                double start() const override { return 0.0; }
            double end() const override { return length_; }

                Eigen::Matrix4d operator()(double u) const { return fn_(u); }

                functor_item* clone_() const override { return new functor_item(*this); }
            virtual kinds kind() const { return FUNCTOR_ITEM; }
            virtual size_t calc_hash() const {
                auto v = std::make_tuple(static_cast<size_t>(FUNCTOR_ITEM), 0);
               return boost::hash<decltype(v)>{}(v);
            }

         private:
                double length_;
                std::function<Eigen::Matrix4d(double u)> fn_;
         };

            struct IFC_GEOM_API piecewise_function : public function_item {
            DECLARE_PTR(piecewise_function)

                using span_list = std::vector<function_item::const_ptr>;

            piecewise_function(double start, const span_list& s, const express::base& instance = express::base());
            piecewise_function(double start, const std::vector<piecewise_function::ptr>& pwfs, const express::base& instance = express::base());
            piecewise_function(piecewise_function&&) = default;
            piecewise_function(const piecewise_function&) = default;
            virtual ~piecewise_function() = default;

                const span_list& spans() const;
            size_t span_count() const {return spans_.size();}
            function_item::const_ptr span_fn(size_t i) { return spans_[i]; }
                bool is_empty() const;
                double start() const override;
                double end() const override;
            double length() const override;

                piecewise_function* clone_() const override { return new piecewise_function(*this); }
                virtual kinds kind() const { return PIECEWISE_FUNCTION; }

                virtual size_t calc_hash() const    {
                    auto v = std::make_tuple(static_cast<size_t>(PIECEWISE_FUNCTION), 0);
                    return boost::hash<decltype(v)>{}(v);
                }

            private:
                double start_ = 0.0; // starting value of the pwf
                span_list spans_;
            };

         struct IFC_GEOM_API gradient_function : public function_item {
             DECLARE_PTR(gradient_function)
             gradient_function(piecewise_function::const_ptr horizontal, piecewise_function::const_ptr vertical, const express::base& instance = express::base());
             gradient_function(gradient_function&&) = default;
             gradient_function(const gradient_function&) = default;
             virtual ~gradient_function() = default;

               virtual double start() const override;
               virtual double end() const override;

                    piecewise_function::const_ptr get_horizontal() const;
               piecewise_function::const_ptr get_vertical() const;

                    gradient_function* clone_() const override { return new gradient_function(*this); }

               virtual kinds kind() const { return GRADIENT_FUNCTION; }

               virtual size_t calc_hash() const {
                  auto v = std::make_tuple(static_cast<size_t>(GRADIENT_FUNCTION), 0);
                  return boost::hash<decltype(v)>{}(v);
               }

            private:
               piecewise_function::const_ptr horizontal_, vertical_;
         };

         struct IFC_GEOM_API cant_function : public function_item {
             DECLARE_PTR(cant_function)
             cant_function(gradient_function::const_ptr gradient, piecewise_function::const_ptr cant, const express::base& instance = express::base());
             cant_function(cant_function&&) = default;
             cant_function(const cant_function&) = default;
             virtual ~cant_function() = default;

             virtual double start() const override;
             virtual double end() const override;

                 gradient_function::const_ptr get_gradient() const;
             piecewise_function::const_ptr get_cant() const;

             cant_function* clone_() const override { return new cant_function(*this); }

             virtual kinds kind() const { return CANT_FUNCTION; }

             virtual size_t calc_hash() const {
                 auto v = std::make_tuple(static_cast<size_t>(CANT_FUNCTION), 0);
                 return boost::hash<decltype(v)>{}(v);
             }

           private:
             gradient_function::const_ptr gradient_;
             piecewise_function::const_ptr cant_;
         };

         struct IFC_GEOM_API offset_function : public function_item {
             DECLARE_PTR(offset_function)
             offset_function(function_item::const_ptr basis, piecewise_function::const_ptr offset, const express::base& instance = express::base());
             offset_function(offset_function&&) = default;
             offset_function(const offset_function&) = default;
             virtual ~offset_function() = default;

             virtual double start() const override;
             virtual double end() const override;

             function_item::const_ptr get_basis() const;
             piecewise_function::const_ptr get_offset() const;

             offset_function* clone_() const override { return new offset_function(*this); }

             virtual kinds kind() const { return OFFSET_FUNCTION; }

             virtual size_t calc_hash() const {
                 auto v = std::make_tuple(static_cast<size_t>(OFFSET_FUNCTION), 0);
                 return boost::hash<decltype(v)>{}(v);
             }

           private:
             function_item::const_ptr basis_;
             piecewise_function::const_ptr offset_;
         };

#ifdef TAXONOMY_USE_SHARED_PTR
            typedef std::shared_ptr<item> ptr;
            typedef std::shared_ptr<const item> const_ptr;
            template<typename T, typename... Args>
            std::shared_ptr<T> make(Args&&... args) {
                return std::make_shared<T>(std::forward<Args>(args)...);
            }
#endif
#ifdef TAXONOMY_USE_UNIQUE_PTR
            typedef std::uniqe_ptr<item> ptr;
            typedef std::uniqe_ptr<const item> ptr;
            template<typename T, typename... Args>
            std::uniqe_ptr<T> make(Args&&... args) {
                return new T(std::forward<Args>(args)...));
            }
#endif
#ifdef TAXONOMY_USE_NAKED_PTR
            typedef item* ptr;
            typedef item const* ptr;
            template<typename T, typename... Args>
            T* make(Args&&... args) {
                return new T(std::forward<Args>(args)...));
            }
#endif

            IFC_GEOM_API bool less(item::const_ptr, item::const_ptr);

            struct less_functor {
                bool operator()(item::const_ptr a, item::const_ptr b) const {
                    return less(a, b);
                }
            };

            struct equal_functor {
                bool operator()(taxonomy::item::ptr const& a,
                    taxonomy::item::ptr const& b) const
                {
                    if (a == b) {
                        return true;
                    }
                    return !less(a, b) && !less(b, a);
                }
            };

            struct hash_functor {
                size_t operator()(taxonomy::item::ptr const& a) const
                {
                    return a->hash();
                }
            };

            // @todo make 4d for easier multiplication
            template <size_t N>
            struct IFC_GEOM_API cartesian_base : public item, public eigen_base<Eigen::Vector3d> {
                cartesian_base() : eigen_base() {}
                cartesian_base(const Eigen::Vector3d& c) : eigen_base(c) {}
                cartesian_base(double x, double y, double z = 0.) : eigen_base(Eigen::Vector3d(x, y, z)) {}
            };

            struct IFC_GEOM_API point3 : public cartesian_base<3> {
                DECLARE_PTR(point3)

                virtual point3* clone_() const { return new point3(*this); }
                virtual kinds kind() const { return POINT3; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(POINT3), hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }

                void print(std::ostream& o, int indent = 0) const;

                point3() : cartesian_base() {}
                point3(const Eigen::Vector3d& c) : cartesian_base(c) {}
                point3(double x, double y, double z = 0.) : cartesian_base(x, y, z) {}
            };

            struct IFC_GEOM_API direction3 : public cartesian_base<3> {
                DECLARE_PTR(direction3)

                virtual direction3* clone_() const { return new direction3(*this); }
                virtual kinds kind() const { return DIRECTION3; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(DIRECTION3), hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }

                void print(std::ostream& o, int indent = 0) const;

                direction3() : cartesian_base() {}
                direction3(const Eigen::Vector3d& c) : cartesian_base(c) {}
                direction3(double x, double y, double z = 0.) : cartesian_base(x, y, z) {}
            };

            struct IFC_GEOM_API curve : public geom_item {
                void print_impl(std::ostream& o, const std::string& classname, int indent = 0) const {
                    o << std::string(indent, ' ') << classname << std::endl;
                    this->matrix->print(o, indent + 4);
                }
            };

            struct IFC_GEOM_API line : public curve {
                DECLARE_PTR(line)

                virtual line* clone_() const { return new line(*this); }
                virtual kinds kind() const { return LINE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(LINE), matrix->hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }

                void print(std::ostream& o, int indent = 0) const;
            };

            struct IFC_GEOM_API circle : public curve {
                DECLARE_PTR(circle)

                double radius;

                virtual circle* clone_() const { return new circle(*this); }
                virtual kinds kind() const { return CIRCLE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(CIRCLE), matrix->hash_components(), radius);
                    return boost::hash<decltype(v)>{}(v);
                }

                void print(std::ostream& o, int indent = 0) const;

                static circle::ptr from_3_points(const Eigen::Vector3d& p1, const Eigen::Vector3d& p2, const Eigen::Vector3d& p3) {
                    Eigen::Vector3d t = p2 - p1;
                    Eigen::Vector3d u = p3 - p1;
                    Eigen::Vector3d v = p3 - p2;

                    auto norm = t.cross(u);
                    auto mag = norm.dot(norm);

                    auto iwsl2 = 1. / (2. * mag);
                    auto tt = t.dot(t);
                    auto uu = u.dot(u);

                    auto orig = p1 + (u * tt * u.dot(v) - t * uu * t.dot(v)) * iwsl2;

                    if (!orig.array().isNaN().any()) {
                        auto radius = std::sqrt(tt * uu * v.dot(v) * iwsl2 * 0.5f);
                        auto ax = norm / std::sqrt(mag);


                        auto c = make<circle>();
                        c->radius = radius;
                        c->matrix = taxonomy::make<taxonomy::matrix4>(orig, ax);
                        return c;
                    }

                    return nullptr;
                }
            };

            struct IFC_GEOM_API ellipse : public curve {
                DECLARE_PTR(ellipse)

                double radius;
                double radius2;

                virtual ellipse* clone_() const { return new ellipse(*this); }
                virtual kinds kind() const { return ELLIPSE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(ELLIPSE), matrix->hash_components(), radius, radius2);
                    return boost::hash<decltype(v)>{}(v);
                }

                void print(std::ostream& o, int indent = 0) const;
            };

            struct IFC_GEOM_API bspline_curve : public curve {
                DECLARE_PTR(bspline_curve)

                virtual bspline_curve* clone_() const { return new bspline_curve(*this); }
                virtual kinds kind() const { return BSPLINE_CURVE; }

                virtual size_t calc_hash() const {
                    size_t h = std::hash<size_t>{}(BSPLINE_CURVE);
                    for (auto& x : control_points) {
                        boost::hash_combine(h, x->hash());
                    }
                    for (auto& x : multiplicities) {
                        boost::hash_combine(h, std::hash<int>{}(x));
                    }
                    for (auto& x : knots) {
                        boost::hash_combine(h, std::hash<double>{}(x));
                    }
                    if (weights) {
                        for (auto& x : *weights) {
                            boost::hash_combine(h, std::hash<double>{}(x));
                        }
                    }
                    boost::hash_combine(h, std::hash<int>{}(degree));
                    return h;
                }

                std::vector<point3::ptr> control_points;
                std::vector<int> multiplicities;
                std::vector<double> knots;
                std::optional<std::vector<double>> weights;
                int degree;
            };

            struct IFC_GEOM_API offset_curve : public curve {
                DECLARE_PTR(offset_curve)

                direction3::ptr reference;
                double offset;
                item::ptr basis;

                virtual offset_curve* clone_() const { return new offset_curve(*this); }
                virtual kinds kind() const { return OFFSET_CURVE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(OFFSET_CURVE), reference->hash(), offset, basis ? basis->hash() : size_t(0));
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API trimmed_curve : public geom_item {
                DECLARE_PTR(trimmed_curve)

                // @todo The copy constructor of point3 within the variant fails on the avx instruction
                // on the default gcc in Ubuntu 18.04 and a recent AMD Ryzen. Probably due to allignment.
                std::variant<boost::blank, point3::ptr, double> start, end;

                // @todo somehow account for the fact that curve in IFC can be trimmed curve, polyline and composite curve as well.
                item::ptr basis;

                // @todo does this make sense? this is to accommodate for the fact that orientation is defined on both TrimmedCurve as well CompCurveSegment
                std::optional<bool> curve_sense;

                trimmed_curve() : basis(nullptr) {}
                trimmed_curve(const point3::ptr& a, const point3::ptr& b) : start(a), end(b), basis(nullptr) {}

                virtual void reverse() {
                    // std::swap(start, end);
                    orientation = !orientation.value_or(true);
                }

                void print(std::ostream& o, int indent = 0) const;
            };

            struct IFC_GEOM_API edge : public trimmed_curve {
                DECLARE_PTR(edge)

                edge() : trimmed_curve() {}
                edge(const point3::ptr& a, const point3::ptr& b) : trimmed_curve(a, b) {}

                // @todo how to express similarity between trimmed_curve and edge?
                virtual edge* clone_() const { return new edge(*this); }
                virtual kinds kind() const { return EDGE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(EDGE), start, end, basis ? basis->hash() : size_t(0), curve_sense ? *curve_sense ? 2 : 1 : 0);
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            template <typename T = item>
            struct IFC_GEOM_API collection_base : public geom_item {
                std::vector<typename T::ptr> children;

                collection_base() {}
                collection_base(const collection_base& other)
                    : geom_item()
                {
                    std::transform(other.children.begin(), other.children.end(), std::back_inserter(children), [](typename T::ptr p) { return clone(p); });
                }

                /*
                template <typename T>
                std::vector<typename T::ptr> children_as() const {
                    std::vector<typename T::ptr> ts;
                    ts.reserve(children.size());
                    std::for_each(children.begin(), children.end(), [&ts](ptr i){
                        auto v = dcast<T>(i);
                        if (v) {
                            ts.push_back(v);
                        }
                    });
                    return ts;
                }
                */

                virtual void reverse() {
                    // @todo this needs to create copies of the children in case of shared_ptr
                    std::reverse(children.begin(), children.end());
                    for (auto& child : children) {
                        child->reverse();
                    }
                }

                virtual void print_impl(std::ostream&, int) const {
                    // empty on purpose
                }

                void print(std::ostream& o, int indent = 0) const {
                    o << std::string(indent, ' ') << kind_to_string(kind()) << std::endl;
                    if (matrix && !matrix->is_identity()) {
                        matrix->print(o, indent + 4);
                    }
                    for (auto& c : children) {
                        c->print(o, indent + 4);
                    }
                    print_impl(o, indent + 4);
                }

                virtual ~collection_base() {
#ifdef TAXONOMY_USE_NAKED_PTR
                    for (auto& c : children) {
                        delete c;
                    }
#endif
                }

                uint32_t hash_elements() const {
                    size_t h = 0;
                    for (auto& c : children) {
                        boost::hash_combine(h, c->hash());
                    }
                    // @todo should we really use uint32_t instead of size_t for hashes?
                    return (uint32_t) h;
                }
            };

            struct IFC_GEOM_API collection : public collection_base<geom_item> {
                DECLARE_PTR(collection)

                virtual collection* clone_() const { return new collection(*this); }
                virtual kinds kind() const { return COLLECTION; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(COLLECTION), hash_elements());
                    return boost::hash<decltype(v)>{}(v);
                }
            };


            struct IFC_GEOM_API loop : public collection_base<edge> {
                DECLARE_PTR(loop)

                std::optional<bool> external, closed;
                std::optional<taxonomy::function_item::ptr> fi;
                std::optional<std::vector<std::string>> tags;

                bool is_polyhedron() const {
                    for (auto& e : children) {
                        if (e->basis != nullptr) {
                            if (e->basis->kind() != LINE) {
                                return false;
                            }
                        }
                    }
                    return true;
                }

                void calculate_linear_edge_curves() const {
                    for (auto& e : children) {
                        if (e->basis == nullptr) {
                            if (e->start.index() == 1 && e->end.index() == 1) {
                                auto ln = make<taxonomy::line>();
                                auto a = std::get<point3::ptr>(e->start)->ccomponents();
                                auto b = std::get<point3::ptr>(e->end)->ccomponents();
                                ln->matrix = make<matrix4>(a, b - a);
                                e->basis = ln;
                            }
                        }
                    }
                }

                void remove_linear_edge_curves() const {
                    for (auto& e : children) {
                        if (e->basis != nullptr && e->basis->kind() == LINE) {
                            e->basis = nullptr;
                        }
                    }
                }

                virtual loop* clone_() const { return new loop(*this); }
                virtual kinds kind() const { return LOOP; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(LOOP), hash_elements(), external ? *external ? 2 : 1 : 0, closed ? *closed ? 2 : 1 : 0);
                    return boost::hash<decltype(v)>{}(v);
                }

                // nb only takes into account explicit points
                taxonomy::point3::ptr centroid() const {
                    Eigen::Vector3d c(0, 0, 0);
                    for (auto& e : children) {
                        if (e->start.index() == 1) {
                            c += std::get<point3::ptr>(e->start)->ccomponents();
                        }
                        if (e->end.index() == 1) {
                            c += std::get<point3::ptr>(e->end)->ccomponents();
                        }
                    }
                    c /= static_cast<double>(children.size());
                    return make<taxonomy::point3>(c);
                }
            };

            struct IFC_GEOM_API face : public collection_base<loop> {
                DECLARE_PTR(face)

                item::ptr basis;

                virtual face* clone_() const { return new face(*this); }
                virtual kinds kind() const { return FACE; }

                virtual void print_impl(std::ostream& o, int indent) const {
                    if (basis) {
                        o << std::string(indent, ' ') << "basis" << std::endl;
                        basis->print(o, indent + 4);
                    }
                }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(FACE), hash_elements(), basis ? basis->hash() : size_t(0));
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API shell : public collection_base<face> {
                DECLARE_PTR(shell)

                std::optional<bool> closed;

                virtual void print_impl(std::ostream& o, int indent) const {
                    using namespace std::string_literals;
                    o << std::string(indent, ' ') << "closed " << (closed ? *closed ? "yes"s : "no"s : "unknown"s) << std::endl;
                }

                virtual shell* clone_() const { return new shell(*this); }
                virtual kinds kind() const { return SHELL; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(SHELL), hash_elements(), closed ? *closed ? 2 : 1 : 0);
                    return boost::hash<decltype(v)>{}(v);
                }

                // nb only takes into account explicit points
                taxonomy::point3::ptr centroid() const {
                    Eigen::Vector3d c(0, 0, 0);
                    for (auto& f : children) {
                        for (auto& l : f->children) {
                            for (auto& e : l->children) {
                                if (e->start.index() == 1) {
                                    c += std::get<point3::ptr>(e->start)->ccomponents();
                                }
                                if (e->end.index() == 1) {
                                    c += std::get<point3::ptr>(e->end)->ccomponents();
                                }
                            }
                        }
                    }
                    c /= static_cast<double>(children.size());
                    return make<taxonomy::point3>(c);
                }
            };

            struct IFC_GEOM_API solid : public collection_base<shell> {
                DECLARE_PTR(solid)

                virtual solid* clone_() const { return new solid(*this); }
                virtual kinds kind() const { return SOLID; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(SOLID), hash_elements());
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API loft : public collection_base<geom_item> {
                DECLARE_PTR(loft)

                item::ptr axis;

                virtual loft* clone_() const { return new loft(*this); }
                virtual kinds kind() const { return LOFT; }

                virtual void print_impl(std::ostream& o, int indent) const {
                    o << std::string(indent, ' ') << "axis" << std::endl;
                    axis->print(o, indent + 4);
                }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(LOFT), hash_elements(), axis ? axis->hash() : size_t(0));
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API surface : public geom_item {};

            struct IFC_GEOM_API plane : public surface {
                DECLARE_PTR(plane)

                virtual plane* clone_() const { return new plane(*this); }
                virtual kinds kind() const { return PLANE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(PLANE), matrix->hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API cylinder : public surface {
                DECLARE_PTR(cylinder)

                double radius;

                virtual cylinder* clone_() const { return new cylinder(*this); }
                virtual kinds kind() const { return CYLINDER; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(CYLINDER), matrix->hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API sphere : public surface {
                DECLARE_PTR(sphere)

                double radius;

                virtual sphere* clone_() const { return new sphere(*this); }
                virtual kinds kind() const { return SPHERE; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(SPHERE), matrix->hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API torus : public surface {
                DECLARE_PTR(torus)

                double radius1;
                double radius2;

                virtual torus* clone_() const { return new torus(*this); }
                virtual kinds kind() const { return TORUS; }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(TORUS), matrix->hash_components());
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API bspline_surface : public surface {
                DECLARE_PTR(bspline_surface)

                virtual bspline_surface* clone_() const { return new bspline_surface(*this); }
                virtual kinds kind() const { return BSPLINE_SURFACE; }

                virtual size_t calc_hash() const {
                    size_t h = std::hash<size_t>{}(BSPLINE_SURFACE);
                    boost::hash_combine(h, std::hash<size_t>{}(control_points.size()));
                    for (auto& xs : control_points) {
                        for (auto& x : xs) {
                            boost::hash_combine(h, x->hash());
                        }
                    }
                    for (auto& xs : multiplicities) {
                        for (auto& x : xs) {
                            boost::hash_combine(h, std::hash<int>{}(x));
                        }
                    }
                    for (auto& xs : knots) {
                        for (auto& x : xs) {
                            boost::hash_combine(h, std::hash<double>{}(x));
                        }
                    }
                    if (weights) {
                        for (auto& xs : *weights) {
                            for (auto& x : xs) {
                                boost::hash_combine(h, std::hash<double>{}(x));
                            }
                        }
                    }
                    boost::hash_combine(h, std::hash<int>{}(degree[0]));
                    boost::hash_combine(h, std::hash<int>{}(degree[1]));
                    return h;
                }

                std::vector<std::vector<point3::ptr>> control_points;
                std::array<std::vector<int>, 2> multiplicities;
                std::array<std::vector<double>, 2> knots;
                std::optional<std::vector<std::vector<double>>> weights;
                std::array<int, 2> degree;
            };

            struct IFC_GEOM_API sweep : public geom_item {
                DECLARE_PTR(sweep)

                item::ptr basis;

                sweep(face::ptr b) : basis(b) {}
                sweep(matrix4::ptr m, item::ptr b) : geom_item(m), basis(b) {}
            };

            struct IFC_GEOM_API extrusion : public sweep {
                DECLARE_PTR(extrusion)

                direction3::ptr direction;
                double depth;

                virtual extrusion* clone_() const { return new extrusion(*this); }
                virtual kinds kind() const { return EXTRUSION; }

                extrusion(matrix4::ptr m, item::ptr basis, direction3::ptr dir, double d) : sweep(m, basis), direction(dir), depth(d) {}

                void print(std::ostream& o, int indent = 0) const;

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(EXTRUSION), matrix->hash_components(), basis->calc_hash(), direction->hash_components(), depth);
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API revolve : public sweep {
                DECLARE_PTR(revolve)

                point3::ptr axis_origin;
                direction3::ptr direction;
                std::optional<double> angle;

                virtual revolve* clone_() const { return new revolve(*this); }
                virtual kinds kind() const { return REVOLVE; }

                revolve(matrix4::ptr m, item::ptr basis, point3::ptr pnt, direction3::ptr dir, const std::optional<double>& a) : sweep(m, basis), axis_origin(pnt), direction(dir), angle(a) {}

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(REVOLVE), matrix->hash_components(), basis->calc_hash(), axis_origin->hash_components(), direction->hash_components(), angle ? *angle : 1000.);
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API sweep_along_curve : public sweep {
                DECLARE_PTR(sweep_along_curve)

                item::ptr surface;
                item::ptr curve;
                direction3::ptr direction = nullptr;

                virtual sweep_along_curve* clone_() const { return new sweep_along_curve(*this); }
                virtual kinds kind() const { return SWEEP_ALONG_CURVE; }

                sweep_along_curve(matrix4::ptr m, face::ptr basis, item::ptr surf, item::ptr crv) : sweep(m, basis), surface(surf), curve(crv), direction(nullptr) {}

                // New constructor for fixed reference swept area solid
                sweep_along_curve(matrix4::ptr m, face::ptr profile, item::ptr directrix, direction3::ptr ref) : sweep(m, profile), surface(nullptr), curve(directrix), direction(ref) { }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(SWEEP_ALONG_CURVE), matrix->hash_components(), basis->calc_hash(), surface->calc_hash(), curve->calc_hash());
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API node : public item {
                DECLARE_PTR(node)

                // std::map<std::string, geom_item> representations;

                virtual node* clone_() const { return new node(*this); }
                virtual kinds kind() const { return NODE; }

                void print(std::ostream&, int = 0) const {}

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(NODE));
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            struct IFC_GEOM_API boolean_result : public collection_base<geom_item> {
                DECLARE_PTR(boolean_result)

                enum operation_type {
                    UNION, SUBTRACTION, INTERSECTION
                };

                virtual boolean_result* clone_() const { return new boolean_result(*this); }
                virtual kinds kind() const { return BOOLEAN_RESULT; }
                operation_type operation;

                static const std::string& operation_str(operation_type op) {
                    using namespace std::string_literals;
                    static std::string s[] = { "union"s, "subtraction"s, "intersection"s };
                    return s[(size_t)op];
                }

                virtual size_t calc_hash() const {
                    auto v = std::make_tuple(static_cast<size_t>(BOOLEAN_RESULT), hash_elements(), static_cast<size_t>(operation));
                    return boost::hash<decltype(v)>{}(v);
                }
            };

            namespace impl {
                typedef std::tuple<matrix4, point3, direction3, line, circle, ellipse, bspline_curve, offset_curve, plane, cylinder, sphere, torus, bspline_surface, edge, loop, face, shell, solid, loft, extrusion, revolve, sweep_along_curve, node, collection, boolean_result, function_item, functor_item, piecewise_function, gradient_function, cant_function,offset_function> kinds_tuple;
                typedef std::tuple<line, circle, ellipse, bspline_curve, offset_curve, loop, edge> curves_tuple;
                typedef std::tuple<plane, cylinder, sphere, torus, bspline_surface, extrusion, revolve> surfaces_tuple;
                typedef std::tuple<edge, loop, face, piecewise_function> upgrades_tuple;
            }

            struct type_by_kind {
                template <std::size_t N>
                using type = typename std::tuple_element<N, impl::kinds_tuple>::type;

                static const size_t max = std::tuple_size<impl::kinds_tuple>::value;
            };

            struct curves {
                template <std::size_t N>
                using type = typename std::tuple_element<N, impl::curves_tuple>::type;

                static const size_t max = std::tuple_size<impl::curves_tuple>::value;
            };

            struct surfaces {
                template <std::size_t N>
                using type = typename std::tuple_element<N, impl::surfaces_tuple>::type;

                static const size_t max = std::tuple_size<impl::surfaces_tuple>::value;
            };

            struct upgrades {
                template <std::size_t N>
                using type = typename std::tuple_element<N, impl::upgrades_tuple>::type;

                static const size_t max = std::tuple_size<impl::upgrades_tuple>::value;
            };

            IFC_GEOM_API std::optional<face::ptr> loop_to_face_upgrade_impl(ptr item);
            template <typename T>
            class loop_to_face_upgrade {
            private:
                std::optional<taxonomy::face::ptr> face_;
            public:
                loop_to_face_upgrade(taxonomy::ptr item) {
                    if constexpr (std::is_same_v<T, face>) {
                        face_ = loop_to_face_upgrade_impl(item);
                    }
                }

                operator bool() const {
                    return face_.has_value();
                }

                operator typename T::ptr() const {
                    if constexpr (std::is_same_v<T, face>) {
                        if (face_) {
                            return *face_;
                        }
                    }
                    return nullptr;
                }
            };

            IFC_GEOM_API std::optional<edge::ptr> curve_to_edge_upgrade_impl(ptr item);
            template <typename T>
            class curve_to_edge_upgrade {
            private:
                std::optional<taxonomy::edge::ptr> edge_;
            public:
                curve_to_edge_upgrade(taxonomy::ptr item) {
                    if constexpr (std::is_same_v<T, edge>) {
                        edge_ = taxonomy::curve_to_edge_upgrade_impl(item);
                    }
                }

                operator bool() const {
                    return edge_.has_value();
                }

                operator typename T::ptr() const {
                    if constexpr (std::is_same_v<T, edge>) {
                        if (edge_) {
                            return *edge_;
                        }
                    }
                    return nullptr;
                }
            };

            IFC_GEOM_API std::optional<loop::ptr> curve_to_loop_upgrade_impl(ptr item);
            template <typename T>
            class curve_to_loop_upgrade {
            private:
                std::optional<taxonomy::loop::ptr> loop_;
            public:
                curve_to_loop_upgrade(taxonomy::ptr item) {
                    if constexpr (std::is_same_v<T, loop>) {
                        loop_ = curve_to_loop_upgrade_impl(item);
                    }
                }

                operator bool() const {
                    return loop_.has_value();
                }

                operator typename T::ptr() const {
                    if constexpr (std::is_same_v<T, loop>) {
                        if (loop_) {
                            return *loop_;
                        }
                    }
                    return nullptr;
                }
            };

            IFC_GEOM_API std::optional<loop::ptr> edge_to_loop_upgrade_impl(ptr item);
            template <typename T>
            class edge_to_loop_upgrade {
            private:
                std::optional<taxonomy::loop::ptr> loop_;
            public:
                edge_to_loop_upgrade(taxonomy::ptr item) {
                    if constexpr (std::is_same_v<T, loop>) {
                        loop_ = edge_to_loop_upgrade_impl(item);
                    }
                }

                operator bool() const {
                    return loop_.has_value();
                }

                operator typename T::ptr() const {
                    if constexpr (std::is_same_v<T, loop>) {
                        if (loop_) {
                            return *loop_;
                        }
                    }
                    return nullptr;
                }
            };

            IFC_GEOM_API std::optional<face::ptr> curve_to_face_upgrade_impl(ptr item);
            template <typename T>
            class curve_to_face_upgrade {
            private:
                std::optional<taxonomy::face::ptr> face_;
            public:
                curve_to_face_upgrade(taxonomy::ptr item) {
                    if constexpr (std::is_same_v<T, edge>) {
                        face_ = curve_to_face_upgrade_impl(item);
                    }
                }

                operator bool() const {
                    return face_.has_value();
                }

                operator typename T::ptr() const {
                    if constexpr (std::is_same_v<T, face>) {
                        if (face_) {
                            return *face_;
                        }
                    }
                    return nullptr;
                }
            };

            IFC_GEOM_API std::optional<function_item::ptr> loop_to_function_item_upgrade_impl(ptr item);
            template <typename T>
            class loop_to_function_item_upgrade {
              private:
                std::optional<taxonomy::function_item::ptr> fi_;

              public:
               loop_to_function_item_upgrade(taxonomy::ptr item) {
                    if constexpr (std::is_same_v<T, function_item>) {
                        fi_ = loop_to_function_item_upgrade_impl(item);
                    }
                }

                operator bool() const {
                    return fi_.has_value();
                }

                operator typename T::ptr() const {
                    if constexpr (std::is_same_v<T, function_item>) {
                        if (fi_) {
                            return *fi_;
                        }
                    }
                    return nullptr;
                }
            };

#ifdef TAXONOMY_USE_SHARED_PTR
            template <typename T, typename U>
            std::shared_ptr<T> cast(const std::shared_ptr<U>& u) {
                {
                    curve_to_edge_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    curve_to_loop_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    curve_to_face_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    edge_to_loop_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    loop_to_face_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    loop_to_function_item_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                if (auto r = std::dynamic_pointer_cast<T>(u)) {
                    return r;
                } else {
                    throw std::runtime_error("Unexpected topology");
                }
            }
            template <typename T, typename U>
            std::shared_ptr<T> dcast(const std::shared_ptr<U>& u) {
                {
                    curve_to_edge_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    curve_to_loop_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    curve_to_face_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    edge_to_loop_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    loop_to_face_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                {
                    loop_to_function_item_upgrade<T> upg(u);
                    if (upg) {
                        return upg;
                    }
                }
                return std::dynamic_pointer_cast<T>(u);
            }
#endif
#ifdef TAXONOMY_USE_UNIQUE_PTR
            template <typename T, typename U>
            T* cast(const std::unique_ptr<U>& u) {
                loop_to_face_upgrade<T> upg(u);
                if (upg) {
                    return upg;
                }
            loop_to_piecewise_function_upgrade<T> pwupg(u);
            if (pwupg) {
               return pwupg;
            }
            return static_cast<T*>(&*u);
            }
            template <typename T, typename U>
            T* dcast(const std::unique_ptr<U>& u) {
                loop_to_face_upgrade<T> upg(u);
                if (upg) {
                    return upg;
                }
            loop_to_piecewise_function_upgrade<T> pwupg(u);
            if (pwupg) {
               return pwupg;
            }
            return dynamic_cast<T*>(&*u);
            }
#endif
#ifdef TAXONOMY_USE_NAKED_PTR
            template <typename T, typename U>
            T* cast(const U*& u) {
                loop_to_face_upgrade<T> upg(u);
                if (upg) {
                    return upg;
                }
            loop_to_piecewise_function_upgrade<T> pwupg(u);
            if (pwupg) {
               return pwupg;
            }
            return std::static_cast<T*>(u);
            }
            template <typename T, typename U>
            T* dcast(const U*& u) {
                loop_to_face_upgrade<T> upg(u);
                if (upg) {
                    return upg;
                }
            loop_to_piecewise_function_upgrade<T> pwupg(u);
            if (pwupg) {
               return pwupg;
            }
            return std::dynamic_cast<T*>(u);
            }
#endif

        }

        template <typename U, typename Fn>
        void visit(const typename U::ptr& deep, Fn fn) {
            for (auto& i : deep->children) {
                // @todo Sad... now that we have templated collection members,
                // we can't generally use collection_base anymore as a cast target.
                if (auto collection = std::dynamic_pointer_cast<taxonomy::collection>(i)) {
                    ifcopenshell::geom::visit<taxonomy::collection>(collection, fn);
                } else if (auto loop = std::dynamic_pointer_cast<taxonomy::loop>(i)) {
                    ifcopenshell::geom::visit<taxonomy::loop>(loop, fn);
                } else if (auto face = std::dynamic_pointer_cast<taxonomy::face>(i)) {
                    ifcopenshell::geom::visit<taxonomy::face>(face, fn);
                } else if (auto shell = std::dynamic_pointer_cast<taxonomy::shell>(i)) {
                    ifcopenshell::geom::visit<taxonomy::shell>(shell, fn);
                } else if (auto solid = std::dynamic_pointer_cast<taxonomy::solid>(i)) {
                    ifcopenshell::geom::visit<taxonomy::solid>(solid, fn);
                } else if (auto loft = std::dynamic_pointer_cast<taxonomy::loft>(i)) {
                    ifcopenshell::geom::visit<taxonomy::loft>(loft, fn);
                } else if (auto boolean_result = std::dynamic_pointer_cast<taxonomy::boolean_result>(i)) {
                    ifcopenshell::geom::visit<taxonomy::boolean_result>(boolean_result, fn);
                }
                else {
                    fn(i);
                }
            }
        }

        template <typename T, typename U, typename Fn>
        void visit_2(const typename U::ptr& collection, const Fn& fn) {
            static_assert(std::is_same<T, taxonomy::point3>::value, "@todo Only implemented for point3");
            for (auto& child : collection->children) {
                // @todo Sad... now that we have templated collection members,
                // we can't generally use collection_base anymore as a cast target.
                if (auto col = std::dynamic_pointer_cast<taxonomy::collection>(child)) {
                    visit_2<T, taxonomy::collection>(col, fn);
                } else if (auto loop = std::dynamic_pointer_cast<taxonomy::loop>(child)) {
                    visit_2<T, taxonomy::loop>(loop, fn);
                } else if (auto face = std::dynamic_pointer_cast<taxonomy::face>(child)) {
                    visit_2<T, taxonomy::face>(face, fn);
                } else if (auto shell = std::dynamic_pointer_cast<taxonomy::shell>(child)) {
                    visit_2<T, taxonomy::shell>(shell, fn);
                } else if (auto solid = std::dynamic_pointer_cast<taxonomy::solid>(child)) {
                    visit_2<T, taxonomy::solid>(solid, fn);
                } else if (auto loft = std::dynamic_pointer_cast<taxonomy::loft>(child)) {
                    visit_2<T, taxonomy::loft>(loft, fn);
                } else if (auto bl = std::dynamic_pointer_cast<taxonomy::boolean_result>(child)) {
                    visit_2<T, taxonomy::boolean_result>(bl, fn);
                } else if (auto pt = std::dynamic_pointer_cast<taxonomy::point3>(child)) {
                    fn(pt);
                } else if (auto ed = std::dynamic_pointer_cast<taxonomy::edge>(child)) {
                    // @todo maybe make edge a collection then as well?
                    if (ed->start.index() == 1) {
                        fn(std::get<taxonomy::point3::ptr>(ed->start));
                    }
                    if (ed->end.index() == 1) {
                        fn(std::get<taxonomy::point3::ptr>(ed->end));
                    }
                }
            }
        }

        IFC_GEOM_API taxonomy::collection::ptr flatten(const taxonomy::collection::ptr& deep);

        template <typename Fn>
        bool apply_predicate_to_collection(const taxonomy::ptr& i, Fn fn) {
            if (i->kind() == taxonomy::COLLECTION) {
                auto c = taxonomy::cast<taxonomy::collection>(i);
                for (auto& child : c->children) {
                    if (apply_predicate_to_collection(child, fn)) {
                        return true;
                    }
                }
                return false;
            }
            else {
                return fn(i);
            }
        }

        // @nb traverses nested collections
        template <typename Fn>
        taxonomy::collection::ptr filter(const taxonomy::collection::ptr& collection, Fn fn) {
            auto filtered = taxonomy::make<taxonomy::collection>();
            for (auto& child : collection->children) {
                if (apply_predicate_to_collection(child, fn)) {
                    filtered->children.push_back(clone(child));
                }
            }
            if (filtered->children.empty()) {
#ifdef TAXONOMY_USE_NAKED_PTR
                delete filtered;
#endif
                return nullptr;
            }
            return filtered;
        }

        // @nb traverses nested collections
        template <typename Fn>
        taxonomy::collection::ptr filter_in_place(taxonomy::collection::ptr collection, Fn fn) {
            auto& c = collection->children;
            auto new_end = std::remove_if(c.begin(), c.end(), [fn](taxonomy::geom_item::ptr i) {
                return !apply_predicate_to_collection(i, fn);
            });
#ifdef TAXONOMY_USE_NAKED_PTR
            for (auto it = new_end; it != c.end(); ++it) {
                delete *it;
            }
#endif
            c.erase(new_end, c.end());
            return collection;
        }

        IFC_GEOM_API taxonomy::solid::ptr create_box(double dx, double dy, double dz);
        IFC_GEOM_API taxonomy::solid::ptr create_box(double x, double y, double z, double dx, double dy, double dz);

        struct IFC_GEOM_API layerset_information {
            std::vector<double> thicknesses;
            std::vector<ifcopenshell::geom::taxonomy::ptr> layers;
            std::vector<ifcopenshell::geom::taxonomy::style> styles;
        };

        enum connection_type {
            ATPATH,
            ATSTART,
            ATEND,
            NOTDEFINED
        };

        typedef std::tuple<connection_type, connection_type, express::base> endpoint_connection;
    }

}

#endif