diff --git a/src/core/include/units/kind.h b/src/core/include/units/kind.h
deleted file mode 100644
index 690dcbd5..00000000
--- a/src/core/include/units/kind.h
+++ /dev/null
@@ -1,68 +0,0 @@
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-#include <units/bits/basic_concepts.h>
-#include <units/bits/external/downcasting.h>
-
-namespace units {
-
-template<Dimension D>
-struct dynamic_origin;
-
-namespace detail {
-
-template<typename K, Dimension D>
-struct _kind_base : downcast_base<_kind_base<K, D>> {
-  using base_kind = K;
-  using dimension = D;
-};
-
-template<Kind K, PointOrigin O>
-struct _point_kind_base : downcast_base<_point_kind_base<K, O>> {
-  using base_kind = K;
-  using dimension = typename K::dimension;
-  using origin = O;
-};
-
-}  // namespace detail
-
-template<Kind K, Dimension D>
-  requires Kind<downcast<detail::_kind_base<typename K::base_kind, D>>>
-using downcast_kind = downcast<detail::_kind_base<typename K::base_kind, D>>;
-
-template<Kind K, PointOrigin O = dynamic_origin<typename K::dimension>>
-  requires PointKind<downcast<detail::_point_kind_base<K, O>>>
-using downcast_point_kind = downcast<detail::_point_kind_base<K, O>>;
-
-template<typename K, Dimension D>
-struct kind : downcast_dispatch<K, detail::_kind_base<K, D>> {};
-
-template<typename DK, Dimension D, Kind BK>
-  requires std::same_as<BK, typename BK::base_kind>
-struct derived_kind : downcast_dispatch<DK, detail::_kind_base<BK, D>> {};
-
-template<typename DPK, Kind BK, PointOrigin O = dynamic_origin<typename BK::dimension>>
-struct point_kind : downcast_dispatch<DPK, detail::_point_kind_base<BK, O>> {};
-
-}  // namespace units
diff --git a/src/core/include/units/quantity_kind.h b/src/core/include/units/quantity_kind.h
deleted file mode 100644
index a47fd547..00000000
--- a/src/core/include/units/quantity_kind.h
+++ /dev/null
@@ -1,409 +0,0 @@
-
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-// IWYU pragma: begin_exports
-#include <units/kind.h>
-#include <units/quantity.h>
-// IWYU pragma: end_exports
-
-#include <concepts>
-#include <type_traits>
-#include <utility>
-
-namespace units {
-
-namespace detail {
-
-template<Kind K>
-inline constexpr auto make_quantity_kind_fn = [](auto&& q) {
-  using Q = std::remove_reference_t<decltype(q)>;
-  return quantity_kind<K, typename Q::unit, typename Q::rep>(std::forward<decltype(q)>(q));
-};
-
-template<QuantityKind QK>
-inline constexpr auto& make_quantity_kind = make_quantity_kind_fn<typename QK::kind_type>;
-
-template<Kind K>
-inline constexpr auto downcasted_kind_fn = [](auto q) {
-  using Q = decltype(q);
-  return make_quantity_kind_fn<downcast_kind<K, typename Q::dimension>>(std::move(q));
-};
-
-template<QuantityKind QK>
-inline constexpr auto& downcasted_kind = downcasted_kind_fn<typename QK::kind_type::base_kind>;
-
-template<typename T, typename K>
-concept quantity_kind_one = QuantityKind<T> && equivalent<typename T::kind_type, downcast_kind<K, dim_one>> &&
-                            detail::quantity_one<typename T::quantity_type>;
-
-}  // namespace detail
-
-/**
- * @brief A concept matching two related quantity kinds
- *
- * Satisfied by quantity kinds having equivalent base kinds.
- */
-template<typename QK1, typename QK2>
-concept QuantityKindRelatedTo = QuantityKind<QK1> && QuantityKind<QK2> &&
-                                equivalent<typename QK1::kind_type::base_kind, typename QK2::kind_type::base_kind>;
-
-/**
- * @brief A quantity kind
- *
- * A quantity with more specific usage as determined by its kind.
- * See https://jcgm.bipm.org/vim/en/1.2.html and NOTE 1 at https://jcgm.bipm.org/vim/en/1.1.html.
- *
- * @tparam K the kind of quantity
- * @tparam U the measurement unit of the quantity kind
- * @tparam Rep the type to be used to represent values of the quantity kind
- */
-template<Kind K, UnitOf<typename K::dimension> U, Representation Rep = double>
-class quantity_kind {
-public:
-  using kind_type = K;
-  using quantity_type = quantity<typename K::dimension, U, Rep>;
-  using dimension = typename quantity_type::dimension;
-  using unit = typename quantity_type::unit;
-  using rep = typename quantity_type::rep;
-  static constexpr units::reference<dimension, unit> reference{};
-
-private:
-  quantity_type q_;
-
-public:
-  quantity_kind() = default;
-  quantity_kind(const quantity_kind&) = default;
-  quantity_kind(quantity_kind&&) = default;
-
-  template<typename T>
-    requires(Quantity<std::remove_cvref_t<T>> || QuantityLike<std::remove_cvref_t<T>> ||
-             (Dimensionless<quantity_type> && !Quantity<std::remove_cvref_t<T>>)) &&
-            std::constructible_from<quantity_type, T>
-  constexpr explicit quantity_kind(T&& t) : q_(std::forward<T>(t))
-  {
-  }
-
-  template<QuantityKindEquivalentTo<quantity_kind> QK2>
-    requires std::convertible_to<typename QK2::quantity_type, quantity_type>
-  constexpr explicit(false) quantity_kind(const QK2& qk) : q_(qk.common())
-  {
-  }
-
-  quantity_kind& operator=(const quantity_kind&) = default;
-  quantity_kind& operator=(quantity_kind&&) = default;
-
-  [[nodiscard]] constexpr quantity_type& common() & noexcept { return q_; }
-  [[nodiscard]] constexpr const quantity_type& common() const& noexcept { return q_; }
-  [[nodiscard]] constexpr quantity_type&& common() && noexcept { return std::move(q_); }
-  [[nodiscard]] constexpr const quantity_type&& common() const&& noexcept { return std::move(q_); }
-
-  [[nodiscard]] static constexpr quantity_kind zero() noexcept
-    requires requires { quantity_type::zero(); }
-  {
-    return quantity_kind(quantity_type::zero());
-  }
-
-  [[nodiscard]] static constexpr quantity_kind one() noexcept
-    requires requires { quantity_type::one(); }
-  {
-    return quantity_kind(quantity_type::one());
-  }
-
-  [[nodiscard]] static constexpr quantity_kind min() noexcept
-    requires requires { quantity_type::min(); }
-  {
-    return quantity_kind(quantity_type::min());
-  }
-
-  [[nodiscard]] static constexpr quantity_kind max() noexcept
-    requires requires { quantity_type::max(); }
-  {
-    return quantity_kind(quantity_type::max());
-  }
-
-  [[nodiscard]] constexpr quantity_kind operator+() const
-    requires requires(quantity_type q) { +q; }
-  {
-    return *this;
-  }
-
-  [[nodiscard]] constexpr QuantityKind auto operator-() const
-    requires requires(quantity_type q) { -q; }
-  {
-    return detail::make_quantity_kind<quantity_kind>(-q_);
-  }
-
-  constexpr quantity_kind& operator++()
-    requires requires(quantity_type q) { ++q; }
-  {
-    ++q_;
-    return *this;
-  }
-
-  [[nodiscard]] constexpr quantity_kind operator++(int)
-    requires requires(quantity_type q) { q++; }
-  {
-    return quantity_kind(q_++);
-  }
-
-  constexpr quantity_kind& operator--()
-    requires requires(quantity_type q) { --q; }
-  {
-    --q_;
-    return *this;
-  }
-
-  [[nodiscard]] constexpr quantity_kind operator--(int)
-    requires requires(quantity_type q) { q--; }
-  {
-    return quantity_kind(q_--);
-  }
-
-  constexpr quantity_kind& operator+=(const quantity_kind& qk)
-    requires requires(quantity_type q) { q += qk.common(); }
-  {
-    q_ += qk.common();
-    return *this;
-  }
-
-  constexpr quantity_kind& operator-=(const quantity_kind& qk)
-    requires requires(quantity_type q) { q -= qk.common(); }
-  {
-    q_ -= qk.common();
-    return *this;
-  }
-
-  template<typename Rep2>
-  constexpr quantity_kind& operator*=(const Rep2& rhs)
-    requires requires(quantity_type q) { q *= rhs; }
-  {
-    q_ *= rhs;
-    return *this;
-  }
-  template<detail::quantity_kind_one<K> QK>
-  constexpr quantity_kind& operator*=(const QK& rhs)
-    requires requires(quantity_type q) { q *= rhs.common(); }
-  {
-    q_ *= rhs.common();
-    return *this;
-  }
-
-  template<typename Rep2>
-  constexpr quantity_kind& operator/=(const Rep2& rhs)
-    requires requires(quantity_type q) { q /= rhs; }
-  {
-    gsl_ExpectsAudit(rhs != quantity_values<Rep2>::zero());
-    q_ /= rhs;
-    return *this;
-  }
-  template<detail::quantity_kind_one<K> QK>
-  constexpr quantity_kind& operator/=(const QK& rhs)
-    requires requires(quantity_type q) { q /= rhs.common(); }
-  {
-    q_ /= rhs.common();
-    return *this;
-  }
-
-  template<typename Rep2>
-  constexpr quantity_kind& operator%=(const Rep2& rhs)
-    requires(!Quantity<Rep2> || Dimensionless<Rep2>) && requires(quantity_type q, const Rep2 r) { q %= r; }
-  {
-    gsl_ExpectsAudit(rhs != quantity_values<Rep2>::zero());
-    q_ %= rhs;
-    return *this;
-  }
-
-  template<QuantityKind QK>
-  constexpr quantity_kind& operator%=(const QK& rhs)
-    requires(QuantityKindEquivalentTo<QK, quantity_kind> || detail::quantity_kind_one<QK, K>) &&
-            requires(quantity_type q) { q %= rhs.common(); }
-  {
-    gsl_ExpectsAudit(rhs.common().number() != quantity_values<typename QK::rep>::zero());
-    q_ %= rhs.common();
-    return *this;
-  }
-
-  // Hidden Friends
-  // Below friend functions are to be found via argument-dependent lookup only
-  template<Representation Value>
-  [[nodiscard]] friend constexpr QuantityKind auto operator*(const quantity_kind& qk, const Value& v)
-    requires requires(quantity_type q) {
-               {
-                 q* v
-                 } -> Quantity;
-             }
-  {
-    return detail::make_quantity_kind<quantity_kind>(qk.common() * v);
-  }
-
-  template<Representation Value>
-  [[nodiscard]] friend constexpr QuantityKind auto operator*(const Value& v, const quantity_kind& qk)
-    requires requires(quantity_type q) {
-               {
-                 v* q
-                 } -> Quantity;
-             }
-  {
-    return detail::make_quantity_kind<quantity_kind>(v * qk.common());
-  }
-
-  template<Representation Value>
-  [[nodiscard]] friend constexpr QuantityKind auto operator/(const quantity_kind& qk, const Value& v)
-    requires requires(quantity_type q) {
-               {
-                 q / v
-                 } -> Quantity;
-             }
-  {
-    gsl_ExpectsAudit(v != quantity_values<Value>::zero());
-    return detail::make_quantity_kind<quantity_kind>(qk.common() / v);
-  }
-
-  template<Representation Value>
-  [[nodiscard]] friend constexpr QuantityKind auto operator/(const Value& v, const quantity_kind& qk)
-    requires requires(quantity_type q) {
-               {
-                 v / q
-                 } -> Quantity;
-             }
-  {
-    gsl_ExpectsAudit(qk.common().number() != quantity_values<rep>::zero());
-    return detail::downcasted_kind<quantity_kind>(v / qk.common());
-  }
-
-  template<Representation Value>
-  [[nodiscard]] friend constexpr QuantityKind auto operator%(const quantity_kind& qk, const Value& v)
-    requires requires(quantity_type q) { q % v; }
-  {
-    gsl_ExpectsAudit(v != quantity_values<Value>::zero());
-    return detail::make_quantity_kind<quantity_kind>(qk.common() % v);
-  }
-
-  [[nodiscard]] friend constexpr auto operator<=>(const quantity_kind& lhs, const quantity_kind& rhs)
-    requires std::three_way_comparable<quantity_type>
-  {
-    return lhs.common() <=> rhs.common();
-  }
-
-  [[nodiscard]] friend constexpr bool operator==(const quantity_kind&, const quantity_kind&) = default;
-};
-
-template<QuantityKind QK1, QuantityKindEquivalentTo<QK1> QK2>
-[[nodiscard]] constexpr QuantityKind auto operator+(const QK1& lhs, const QK2& rhs)
-  requires requires { lhs.common() + rhs.common(); }
-{
-  return detail::make_quantity_kind<QK1>(lhs.common() + rhs.common());
-}
-
-template<QuantityKind QK1, QuantityKindEquivalentTo<QK1> QK2>
-[[nodiscard]] constexpr QuantityKind auto operator-(const QK1& lhs, const QK2& rhs)
-  requires requires { lhs.common() - rhs.common(); }
-{
-  return detail::make_quantity_kind<QK1>(lhs.common() - rhs.common());
-}
-
-template<QuantityKind QK, Quantity Q>
-[[nodiscard]] constexpr QuantityKind auto operator*(const QK& lhs, const Q& rhs)
-  requires requires { lhs.common() * rhs; }
-{
-  return detail::downcasted_kind<QK>(lhs.common() * rhs);
-}
-
-template<Quantity Q, QuantityKind QK>
-[[nodiscard]] constexpr QuantityKind auto operator*(const Q& lhs, const QK& rhs)
-  requires requires { lhs* rhs.common(); }
-{
-  return detail::downcasted_kind<QK>(lhs * rhs.common());
-}
-
-template<QuantityKind QK1, QuantityKindRelatedTo<QK1> QK2>
-[[nodiscard]] constexpr QuantityKind auto operator*(const QK1& lhs, const QK2& rhs)
-  requires requires { lhs.common() * rhs.common(); }
-{
-  return detail::downcasted_kind<QK1>(lhs.common() * rhs.common());
-}
-
-template<QuantityKind QK, Quantity Q>
-[[nodiscard]] constexpr QuantityKind auto operator/(const QK& lhs, const Q& rhs)
-  requires requires { lhs.common() / rhs; }
-{
-  gsl_ExpectsAudit(rhs.number() != quantity_values<typename Q::rep>::zero());
-  return detail::downcasted_kind<QK>(lhs.common() / rhs);
-}
-
-template<Quantity Q, QuantityKind QK>
-[[nodiscard]] constexpr QuantityKind auto operator/(const Q& lhs, const QK& rhs)
-  requires requires { lhs / rhs.common(); }
-{
-  gsl_ExpectsAudit(rhs.common().number() != quantity_values<typename QK::rep>::zero());
-  return detail::downcasted_kind<QK>(lhs / rhs.common());
-}
-
-template<QuantityKind QK1, QuantityKindRelatedTo<QK1> QK2>
-[[nodiscard]] constexpr QuantityKind auto operator/(const QK1& lhs, const QK2& rhs)
-  requires requires { lhs.common() / rhs.common(); }
-{
-  return detail::downcasted_kind<QK1>(lhs.common() / rhs.common());
-}
-
-template<QuantityKind QK, Dimensionless D>
-[[nodiscard]] constexpr QuantityKind auto operator%(const QK& lhs, const D& rhs)
-  requires requires { lhs.common() % rhs; }
-{
-  gsl_ExpectsAudit(rhs.number() != quantity_values<typename D::rep>::zero());
-  return detail::make_quantity_kind<QK>(lhs.common() % rhs);
-}
-
-template<QuantityKind QK1, QuantityKindEquivalentTo<QK1> QK2>
-[[nodiscard]] constexpr QuantityKind auto operator%(const QK1& lhs, const QK2& rhs)
-  requires requires { lhs.common() % rhs.common(); }
-{
-  gsl_ExpectsAudit(rhs.common().number() != quantity_values<typename QK2::rep>::zero());
-  return detail::make_quantity_kind<QK1>(lhs.common() % rhs.common());
-}
-
-template<QuantityKind QK1, QuantityKindEquivalentTo<QK1> QK2>
-  requires std::three_way_comparable_with<typename QK1::quantity_type, typename QK2::quantity_type>
-[[nodiscard]] constexpr auto operator<=>(const QK1& lhs, const QK2& rhs)
-{
-  return lhs.common() <=> rhs.common();
-}
-
-template<QuantityKind QK1, QuantityKindEquivalentTo<QK1> QK2>
-  requires std::equality_comparable_with<typename QK1::quantity_type, typename QK2::quantity_type>
-[[nodiscard]] constexpr bool operator==(const QK1& lhs, const QK2& rhs)
-{
-  return lhs.common() == rhs.common();
-}
-
-// type traits
-namespace detail {
-
-template<typename K, typename U, typename Rep>
-inline constexpr bool is_quantity_kind<quantity_kind<K, U, Rep>> = true;
-
-}  // namespace detail
-
-}  // namespace units
diff --git a/src/core/include/units/quantity_point_kind.h b/src/core/include/units/quantity_point_kind.h
deleted file mode 100644
index 837ab301..00000000
--- a/src/core/include/units/quantity_point_kind.h
+++ /dev/null
@@ -1,202 +0,0 @@
-
-// The MIT License (MIT)
-//
-// Copyright (c) 2018 Mateusz Pusz
-//
-// Permission is hereby granted, free of charge, to any person obtaining a copy
-// of this software and associated documentation files (the "Software"), to deal
-// in the Software without restriction, including without limitation the rights
-// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-// copies of the Software, and to permit persons to whom the Software is
-// furnished to do so, subject to the following conditions:
-//
-// The above copyright notice and this permission notice shall be included in all
-// copies or substantial portions of the Software.
-//
-// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-// SOFTWARE.
-
-#pragma once
-
-// IWYU pragma: begin_exports
-#include <units/quantity_kind.h>
-#include <units/quantity_point.h>
-#include <compare>
-// IWYU pragma: end_exports
-
-namespace units {
-
-/**
- * @brief A quantity point kind
- *
- * An absolute quantity kind measured from an origin.
- *
- * @tparam PK the point kind of quantity point
- * @tparam U the measurement unit of the quantity point kind
- * @tparam Rep the type to be used to represent values of the quantity point kind
- */
-template<PointKind PK, UnitOf<typename PK::dimension> U, Representation Rep = double>
-class quantity_point_kind {
-public:
-  using point_kind_type = PK;
-  using kind_type = typename PK::base_kind;
-  using origin = typename point_kind_type::origin;
-  using quantity_kind_type = quantity_kind<kind_type, U, Rep>;
-  using quantity_type = typename quantity_kind_type::quantity_type;
-  using dimension = typename quantity_type::dimension;
-  using unit = typename quantity_type::unit;
-  using rep = typename quantity_type::rep;
-  static constexpr units::reference<dimension, unit> reference{};
-
-private:
-  quantity_kind_type qk_;
-
-public:
-  quantity_point_kind() = default;
-  quantity_point_kind(const quantity_point_kind&) = default;
-  quantity_point_kind(quantity_point_kind&&) = default;
-
-  template<typename T>
-    requires std::constructible_from<quantity_kind_type, T>
-  constexpr explicit quantity_point_kind(T&& t) : qk_(std::forward<T>(t))
-  {
-  }
-
-  constexpr explicit quantity_point_kind(const quantity_point<origin, U, Rep>& qp) : qk_(qp.relative()) {}
-  constexpr explicit quantity_point_kind(quantity_point<origin, U, Rep>&& qp) : qk_(std::move(qp).relative()) {}
-
-  template<QuantityPointLike QP>
-    requires(std::constructible_from<quantity_point<origin, U, Rep>, QP>)
-  constexpr explicit quantity_point_kind(const QP& qp) : qk_(quantity_point_like_traits<QP>::relative(qp))
-  {
-  }
-
-  template<QuantityPointKindOf<point_kind_type> QPK2>
-    requires std::convertible_to<typename QPK2::quantity_kind_type, quantity_kind_type>
-  constexpr explicit(false) quantity_point_kind(const QPK2& qpk) : qk_(qpk.relative())
-  {
-  }
-
-  quantity_point_kind& operator=(const quantity_point_kind&) = default;
-  quantity_point_kind& operator=(quantity_point_kind&&) = default;
-
-  [[nodiscard]] constexpr quantity_kind_type& relative() & noexcept { return qk_; }
-  [[nodiscard]] constexpr const quantity_kind_type& relative() const& noexcept { return qk_; }
-  [[nodiscard]] constexpr quantity_kind_type&& relative() && noexcept { return std::move(qk_); }
-  [[nodiscard]] constexpr const quantity_kind_type&& relative() const&& noexcept { return std::move(qk_); }
-
-  [[nodiscard]] static constexpr quantity_point_kind min() noexcept
-    requires requires { quantity_kind_type::min(); }
-  {
-    return quantity_point_kind(quantity_kind_type::min());
-  }
-
-  [[nodiscard]] static constexpr quantity_point_kind max() noexcept
-    requires requires { quantity_kind_type::max(); }
-  {
-    return quantity_point_kind(quantity_kind_type::max());
-  }
-
-  constexpr quantity_point_kind& operator++()
-    requires requires(quantity_kind_type qk) { ++qk; }
-  {
-    ++qk_;
-    return *this;
-  }
-
-  [[nodiscard]] constexpr quantity_point_kind operator++(int)
-    requires requires(quantity_kind_type qk) { qk++; }
-  {
-    return quantity_point_kind(qk_++);
-  }
-
-  constexpr quantity_point_kind& operator--()
-    requires requires(quantity_kind_type qk) { --qk; }
-  {
-    --qk_;
-    return *this;
-  }
-
-  [[nodiscard]] constexpr quantity_point_kind operator--(int)
-    requires requires(quantity_kind_type qk) { qk--; }
-  {
-    return quantity_point_kind(qk_--);
-  }
-
-  constexpr quantity_point_kind& operator+=(const quantity_kind_type& qk)
-    requires requires(quantity_kind_type qk1, const quantity_kind_type qk2) { qk1 += qk2; }
-  {
-    qk_ += qk;
-    return *this;
-  }
-
-  constexpr quantity_point_kind& operator-=(const quantity_kind_type& qk)
-    requires requires(quantity_kind_type qk1, const quantity_kind_type qk2) { qk1 -= qk2; }
-  {
-    qk_ -= qk;
-    return *this;
-  }
-
-  // Hidden Friends
-  // Below friend functions are to be found via argument-dependent lookup only
-
-  template<QuantityKind QK>
-  [[nodiscard]] friend constexpr QuantityPointKind auto operator+(const quantity_point_kind& lhs, const QK& rhs)
-    requires requires(quantity_kind_type qk) { qk + rhs; }
-  {
-    return units::quantity_point_kind(lhs.relative() + rhs);
-  }
-
-  template<QuantityKind QK>
-  [[nodiscard]] friend constexpr QuantityPointKind auto operator+(const QK& lhs, const quantity_point_kind& rhs)
-    requires requires(quantity_kind_type qk) { lhs + qk; }
-  {
-    return units::quantity_point_kind(lhs + rhs.relative());
-  }
-
-  template<QuantityKind QK>
-  [[nodiscard]] friend constexpr QuantityPointKind auto operator-(const quantity_point_kind& lhs, const QK& rhs)
-    requires requires(quantity_kind_type qk) { qk - rhs; }
-  {
-    return units::quantity_point_kind(lhs.relative() - rhs);
-  }
-
-  template<QuantityPointKindOf<point_kind_type> QPK>
-  [[nodiscard]] friend constexpr QuantityKind auto operator-(const quantity_point_kind& lhs, const QPK& rhs)
-    requires requires(quantity_kind_type qk) { qk - qk; }
-  {
-    return lhs.relative() - rhs.relative();
-  }
-
-  template<QuantityPointKindOf<point_kind_type> QPK>
-    requires std::three_way_comparable_with<quantity_kind_type, typename QPK::quantity_kind_type>
-  [[nodiscard]] friend constexpr auto operator<=>(const quantity_point_kind& lhs, const QPK& rhs)
-  {
-    return lhs.relative() <=> rhs.relative();
-  }
-
-  template<QuantityPointKindOf<point_kind_type> QPK>
-    requires std::equality_comparable_with<quantity_kind_type, typename QPK::quantity_kind_type>
-  [[nodiscard]] friend constexpr bool operator==(const quantity_point_kind& lhs, const QPK& rhs)
-  {
-    return lhs.relative() == rhs.relative();
-  }
-};
-
-template<QuantityKind QK>
-quantity_point_kind(QK)
-  -> quantity_point_kind<downcast_point_kind<typename QK::kind_type>, typename QK::unit, typename QK::rep>;
-
-namespace detail {
-
-template<typename PK, typename U, typename Rep>
-inline constexpr bool is_quantity_point_kind<quantity_point_kind<PK, U, Rep>> = true;
-
-}  // namespace detail
-
-}  // namespace units