Units library moved to concepts world

src/include/units/bits/stdconcepts.h

@@ -0,0 +1,44 @@
+// 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 <ratio>
+#include <type_traits>
+
+namespace mp {
+
+  namespace detail {
+    template<class T, class U>
+    bool concept SameHelper = std::is_same_v<T, U>;
+  }
+
+  template<class T, class U>
+  bool concept Same = detail::SameHelper<T, U> && detail::SameHelper<U, T>;
+
+  template <class From, class To>
+  bool concept ConvertibleTo = std::is_convertible_v<From, To> &&
+      requires(From (&f)()) {
+          static_cast<To>(f());
+      };
+
+}  // namespace mp

src/include/units/bits/tools.h

@@ -22,16 +22,12 @@
 
 #pragma once
 
+#include "stdconcepts.h"
 #include <ratio>
 #include <type_traits>
 
 namespace mp {
 
-  // Requires
-
-  template<bool B>
-  using Requires = std::enable_if_t<B, bool>;
-
   // static_sign
 
   template<std::intmax_t Pn>
@@ -60,6 +56,8 @@ namespace mp {
 
   // is_ratio
 
+  namespace detail {
+
   template<typename T>
   struct is_ratio : std::false_type {
   };
@@ -68,17 +66,22 @@ namespace mp {
   struct is_ratio<std::ratio<Num, Den>> : std::true_type {
   };
 
+  }
+
+  template<typename T>
+  bool concept Ratio = detail::is_ratio<T>::value;
+
   // common_ratio
 
   // todo: simplified
-  template<typename Ratio1, typename Ratio2>
+  template<Ratio Ratio1, Ratio Ratio2>
   struct common_ratio {
     using gcd_num = static_gcd<Ratio1::num, Ratio2::num>;
     using gcd_den = static_gcd<Ratio1::den, Ratio2::den>;
     using type = std::ratio<gcd_num::value, (Ratio1::den / gcd_den::value) * Ratio2::den>;
   };
 
-  template<typename Ratio1, typename Ratio2>
+  template<Ratio Ratio1, Ratio Ratio2>
   using common_ratio_t = typename common_ratio<Ratio1, Ratio2>::type;
 
 }  // namespace mp

src/include/units/bits/type_list.h

@@ -32,9 +32,22 @@ namespace mp {
   template<typename... Types>
   struct type_list;
 
+  namespace detail {
+
+    template<typename T>
+    struct is_type_list : std::false_type {};
+
+    template<typename... Types>
+    struct is_type_list<type_list<Types...>> : std::true_type {};
+
+  }
+
+  template<typename T>
+  bool concept TypeList = detail::is_type_list<T>::value;
+
   // push_front
 
-  template<typename TypeList, typename... Types>
+  template<TypeList List, typename... Types>
   struct type_list_push_front;
 
   template<typename... OldTypes, typename... NewTypes>
@@ -42,12 +55,12 @@ namespace mp {
     using type = type_list<NewTypes..., OldTypes...>;
   };
 
-  template<typename TypeList, typename... Types>
-  using type_list_push_front_t = typename type_list_push_front<TypeList, Types...>::type;
+  template<TypeList List, typename... Types>
+  using type_list_push_front_t = typename type_list_push_front<List, Types...>::type;
 
   // push_back
 
-  template<typename TypeList, typename... Types>
+  template<TypeList List, typename... Types>
   struct type_list_push_back;
 
   template<typename... OldTypes, typename... NewTypes>
@@ -55,8 +68,8 @@ namespace mp {
     using type = type_list<OldTypes..., NewTypes...>;
   };
 
-  template<typename TypeList, typename... Types>
-  using type_list_push_back_t = typename type_list_push_back<TypeList, Types...>::type;
+  template<TypeList List, typename... Types>
+  using type_list_push_back_t = typename type_list_push_back<List, Types...>::type;
 
   // split
 
@@ -76,17 +89,18 @@ namespace mp {
       using base = split_impl<Idx + 1, N, Rest...>;
       using base_first = typename base::first_list;
       using base_second = typename base::second_list;
-      using first_list = std::conditional_t < Idx<N, type_list_push_front_t<base_first, T>, base_first>;
-      using second_list = std::conditional_t < Idx<N, base_second, type_list_push_front_t<base_second, T>>;
+      using first_list = std::conditional_t<Idx<N, type_list_push_front_t<base_first, T>, base_first>;
+      using second_list = std::conditional_t<Idx<N, base_second, type_list_push_front_t<base_second, T>>;
     };
 
   }  // namespace detail
 
-  template<typename T, std::size_t N>
+  template<TypeList List, std::size_t N>
   struct type_list_split;
 
   template<std::size_t N, typename... Types>
   struct type_list_split<type_list<Types...>, N> {
+    static_assert(N <= sizeof...(Types), "Invalid index provided");
     using split = detail::split_impl<0, N, Types...>;
     using first_list = typename split::first_list;
     using second_list = typename split::second_list;
@@ -94,7 +108,7 @@ namespace mp {
 
   // split_half
 
-  template<typename T>
+  template<TypeList List>
   struct type_list_split_half;
 
   template<typename... Types>
@@ -103,11 +117,11 @@ namespace mp {
 
   // merge_sorted
 
-  template<typename T1, typename T2, template<typename, typename> typename Pred>
+  template<TypeList SortedList1, TypeList SortedList2, template<typename, typename> typename Pred>
   struct type_list_merge_sorted;
 
-  template<typename T1, typename T2, template<typename, typename> typename Pred>
-  using type_list_merge_sorted_t = typename type_list_merge_sorted<T1, T2, Pred>::type;
+  template<TypeList SortedList1, TypeList SortedList2, template<typename, typename> typename Pred>
+  using type_list_merge_sorted_t = typename type_list_merge_sorted<SortedList1, SortedList2, Pred>::type;
 
   template<typename... Lhs, template<typename, typename> typename Pred>
   struct type_list_merge_sorted<type_list<Lhs...>, type_list<>, Pred> {
@@ -132,7 +146,7 @@ namespace mp {
 
   // sort
 
-  template<typename T, template<typename, typename> typename Pred>
+  template<TypeList List, template<typename, typename> typename Pred>
   struct type_list_sort;
 
   template<template<typename, typename> typename Pred>
@@ -154,7 +168,7 @@ namespace mp {
     using type = type_list_merge_sorted_t<left, right, Pred>;
   };
 
-  template<typename T, template<typename, typename> typename Pred>
-  using type_list_sort_t = typename type_list_sort<T, Pred>::type;
+  template<TypeList TypeList, template<typename, typename> typename Pred>
+  using type_list_sort_t = typename type_list_sort<TypeList, Pred>::type;
 
 }  // namespace mp

src/include/units/dimension.h

@@ -35,7 +35,7 @@ namespace units {
   // dim_id_less
 
   template<typename D1, typename D2>
-      struct dim_id_less : std::bool_constant<D1::value<D2::value> {
+      struct dim_id_less : std::bool_constant<D1::value < D2::value> {
   };
 
   // exp
@@ -46,15 +46,30 @@ namespace units {
     static constexpr int value = Value;
   };
 
+  // is_exp
+  namespace detail {
+    template<typename T>
+    struct is_exp : std::false_type {
+    };
+
+    template<typename BaseDim, int Value>
+    struct is_exp<exp<BaseDim, Value>> : std::true_type {
+    };
+  }
+
+  template<typename T>
+  bool concept Exp = detail::is_exp<T>::value;
+
+
   // exp_less
 
-  template<typename E1, typename E2>
+  template<Exp E1, Exp E2>
   struct exp_less : dim_id_less<typename E1::dimension, typename E2::dimension> {
   };
 
   // exp_invert
 
-  template<typename Exponent>
+  template<Exp Exponent>
   struct exp_invert;
 
   template<typename BaseDimension, int Value>
@@ -62,88 +77,96 @@ namespace units {
     using type = exp<BaseDimension, -Value>;
   };
 
-  template<typename Exponent>
+  template<Exp Exponent>
   using exp_invert_t = typename exp_invert<Exponent>::type;
 
   // dimension
 
-  template<typename... Exponents>
+  template<Exp... Exponents>
   using dimension = mp::type_list<Exponents...>;
 
+  // is_dimension
+  namespace detail {
+    template<typename T>
+    struct is_dimension : std::false_type {};
+
+    template<Exp... Exponents>
+    struct is_dimension<dimension<Exponents...>> : std::bool_constant<(is_exp<Exponents>::value && ...)> {};
+  }
+
+  template<typename T>
+  bool concept Dimension = detail::is_dimension<T>::value;
+
+
   // make_dimension
 
   namespace detail {
 
-    struct scalar;
-
-    template<typename D>
+    template<Dimension D>
     struct dim_consolidate;
 
-    template<typename D>
+    template<Dimension D>
     using dim_consolidate_t = typename dim_consolidate<D>::type;
 
     template<>
     struct dim_consolidate<dimension<>> {
-      using type = dimension<scalar>;
+      using type = dimension<>;
     };
 
-    template<typename E1>
-    struct dim_consolidate<dimension<E1>> {
-      using type = dimension<E1>;
+    template<Exp E>
+    struct dim_consolidate<dimension<E>> {
+      using type = dimension<E>;
     };
 
-    template<typename... ERest>
-    struct dim_consolidate<dimension<scalar, ERest...>> {
-      using type = dim_consolidate_t<dimension<ERest...>>;
+    template<Exp E1, Exp... ERest>
+    struct dim_consolidate<dimension<E1, ERest...>> {
+      using rest = dim_consolidate_t<dimension<ERest...>>;
+      using type = std::conditional_t<std::is_same_v<rest, dimension<>>, dimension<E1>,
+                                      mp::type_list_push_front_t<rest, E1>>;
     };
 
-    template<typename D, int V1, int V2, typename... ERest>
+    template<typename D, int V1, int V2, Exp... ERest>
     struct dim_consolidate<dimension<exp<D, V1>, exp<D, V2>, ERest...>> {
       using type = std::conditional_t<V1 + V2 == 0, dim_consolidate_t<dimension<ERest...>>,
                                       dim_consolidate_t<dimension<exp<D, V1 + V2>, ERest...>>>;
     };
 
-    template<typename E1, typename... ERest>
-    struct dim_consolidate<dimension<E1, ERest...>> {
-      using rest = dim_consolidate_t<dimension<ERest...>>;
-      using type = std::conditional_t<std::is_same_v<rest, dimension<scalar>>, dimension<E1>,
-                                      mp::type_list_push_front_t<rest, E1>>;
-    };
-
   }  // namespace detail
 
-  template<typename... Exponents>
+  template<Exp... Exponents>
   struct make_dimension {
-    using type = detail::dim_consolidate_t<mp::type_list_sort_t<mp::type_list<Exponents...>, exp_less>>;
+    using type = detail::dim_consolidate_t<mp::type_list_sort_t<dimension<Exponents...>, exp_less>>;
   };
 
-  template<typename... Exponents>
+  template<Exp... Exponents>
   using make_dimension_t = typename make_dimension<Exponents...>::type;
 
+
+
   // dimension_multiply
 
-  template<typename D1, typename D2>
+  template<Dimension D1, Dimension D2>
   struct dimension_multiply;
 
-  template<typename... Exp1, typename... Exp2>
+  template<Exp... Exp1, Exp... Exp2>
   struct dimension_multiply<dimension<Exp1...>, dimension<Exp2...>> {
     using type = make_dimension_t<Exp1..., Exp2...>;
   };
 
-  template<typename D1, typename D2>
+  template<Dimension D1, Dimension D2>
   using dimension_multiply_t = typename dimension_multiply<D1, D2>::type;
 
   // dimension_divide
 
-  template<typename D1, typename D2>
+  template<Dimension D1, Dimension D2>
   struct dimension_divide;
 
-  template<typename... Exp1, typename... Exp2>
+  template<Exp... Exp1, Exp... Exp2>
   struct dimension_divide<dimension<Exp1...>, dimension<Exp2...>>
       : dimension_multiply<dimension<Exp1...>, dimension<exp_invert_t<Exp2>...>> {
   };
 
-  template<typename D1, typename D2>
+  template<Dimension D1, Dimension D2>
   using dimension_divide_t = typename dimension_divide<D1, D2>::type;
 
 }  // namespace units

src/include/units/quantity.h

@@ -28,23 +28,26 @@
 
 namespace units {
 
-  template<typename Dimension, typename Rep, class Ratio>
-  class quantity;
-
   // is_quantity
 
+  template<Dimension Dimension, typename Rep, mp::Ratio Ratio>
+  class quantity;
+
   namespace detail {
 
     template<typename T>
     struct is_quantity : std::false_type {
     };
 
-    template<typename Dimension, typename Rep, class Ratio>
+    template<Dimension Dimension, typename Rep, mp::Ratio Ratio>
     struct is_quantity<quantity<Dimension, Rep, Ratio>> : std::true_type {
     };
 
   }
 
+  template<typename T>
+  bool concept Quantity = detail::is_quantity<T>::value;
+
   // treat_as_floating_point
 
   template<class Rep>
@@ -57,9 +60,9 @@ namespace units {
 
   namespace detail {
 
-    template<typename To, typename CRatio, typename CRep, bool NumIsOne = false, bool DenIsOne = false>
+    template<Quantity To, mp::Ratio CRatio, typename CRep, bool NumIsOne = false, bool DenIsOne = false>
     struct quantity_cast_impl {
-      template<typename Dimension, typename Rep, typename Ratio>
+      template<Dimension Dimension, typename Rep, mp::Ratio Ratio>
       static constexpr To cast(const quantity<Dimension, Rep, Ratio>& q)
       {
         return To(static_cast<typename To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num) /
@@ -67,27 +70,27 @@ namespace units {
       }
     };
 
-    template<typename To, typename CRatio, typename CRep>
+    template<Quantity To, mp::Ratio CRatio, typename CRep>
     struct quantity_cast_impl<To, CRatio, CRep, true, true> {
-      template<typename Dimension, typename Rep, typename Ratio>
+      template<Dimension Dimension, typename Rep, mp::Ratio Ratio>
       static constexpr To cast(const quantity<Dimension, Rep, Ratio>& q)
       {
         return To(static_cast<typename To::rep>(q.count()));
       }
     };
 
-    template<typename To, typename CRatio, typename CRep>
+    template<Quantity To, mp::Ratio CRatio, typename CRep>
     struct quantity_cast_impl<To, CRatio, CRep, true, false> {
-      template<typename Dimension, typename Rep, typename Ratio>
+      template<Dimension Dimension, typename Rep, mp::Ratio Ratio>
       static constexpr To cast(const quantity<Dimension, Rep, Ratio>& q)
       {
         return To(static_cast<typename To::rep>(static_cast<CRep>(q.count()) / static_cast<CRep>(CRatio::den)));
       }
     };
 
-    template<typename To, typename CRatio, typename CRep>
+    template<Quantity To, mp::Ratio CRatio, typename CRep>
     struct quantity_cast_impl<To, CRatio, CRep, false, true> {
-      template<typename Dimension, typename Rep, typename Ratio>
+      template<Dimension Dimension, typename Rep, mp::Ratio Ratio>
       static constexpr To cast(const quantity<Dimension, Rep, Ratio>& q)
       {
         return To(static_cast<typename To::rep>(static_cast<CRep>(q.count()) * static_cast<CRep>(CRatio::num)));
@@ -96,8 +99,8 @@ namespace units {
 
   }  // namespace detail
 
-  template<typename To, typename Dimension, typename Rep, typename Ratio,
-           mp::Requires<detail::is_quantity<To>::value && std::is_same_v<typename To::dimension, Dimension>> = true>
+  template<Quantity To, Dimension Dimension, typename Rep, mp::Ratio Ratio>
+    requires mp::Same<typename To::dimension, Dimension>
   constexpr To quantity_cast(const quantity<Dimension, Rep, Ratio>& q)
   {
     using c_ratio = std::ratio_divide<Ratio, typename To::ratio>;
@@ -117,7 +120,7 @@ namespace units {
 
   // quantity
 
-  template<typename Dimension, typename Rep, class Ratio = std::ratio<1>>
+  template<Dimension Dimension, typename Rep, mp::Ratio Ratio = std::ratio<1>>
   class quantity {
     Rep value_;
   public:
@@ -126,21 +129,20 @@ namespace units {
     using ratio = Ratio;
 
     static_assert(!detail::is_quantity<Rep>::value, "rep cannot be a quantity");
-    static_assert(mp::is_ratio<ratio>::value, "ratio must be a specialization of std::ratio");
     static_assert(ratio::num > 0, "ratio must be positive");
 
     quantity() = default;
     quantity(const quantity&) = default;
 
-    template<class Rep2, mp::Requires<std::is_convertible_v<Rep2, rep> &&
-                                     (treat_as_floating_point_v<rep> || !treat_as_floating_point_v<Rep2>)> = true>
+    template<class Rep2>
+      requires mp::ConvertibleTo<Rep2, rep> && (treat_as_floating_point_v<rep> || !treat_as_floating_point_v<Rep2>)
     constexpr explicit quantity(const Rep2& r) : value_{static_cast<rep>(r)}
     {
     }
 
-    template<class Rep2, class Ratio2,
-             mp::Requires<treat_as_floating_point_v<rep> ||
-                         (std::ratio_divide<Ratio2, ratio>::den == 1 && !treat_as_floating_point<Rep2>::value)> = true>
+    template<class Rep2, mp::Ratio Ratio2>
+      requires mp::ConvertibleTo<Rep2, rep> && (treat_as_floating_point_v<rep> ||
+               (std::ratio_divide<Ratio2, ratio>::den == 1 && !treat_as_floating_point_v<Rep2>))
     constexpr quantity(const quantity<Dimension, Rep2, Ratio2>& q) : value_{quantity_cast<quantity>(q).count()}
     {
     }
@@ -208,7 +210,7 @@ namespace units {
   };
 
   // clang-format off
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   std::common_type_t<quantity<Dimension, Rep1, Ratio1>, quantity<Dimension, Rep2, Ratio2>>
   constexpr operator+(const quantity<Dimension, Rep1, Ratio1>& lhs,
                       const quantity<Dimension, Rep2, Ratio2>& rhs)
@@ -217,7 +219,7 @@ namespace units {
     return ret(ret(lhs).count() + ret(rhs).count());
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   std::common_type_t<quantity<Dimension, Rep1, Ratio1>, quantity<Dimension, Rep2, Ratio2>>
   constexpr operator-(const quantity<Dimension, Rep1, Ratio1>& lhs,
                       const quantity<Dimension, Rep2, Ratio2>& rhs)
@@ -226,7 +228,7 @@ namespace units {
     return ret(ret(lhs).count() - ret(rhs).count());
   }
 
-  template<typename Dimension, typename Rep1, class Ratio, typename Rep2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio, typename Rep2>
   quantity<Dimension, std::common_type_t<Rep1, Rep2>, Ratio>
   constexpr operator*(const quantity<Dimension, Rep1, Ratio>& q,
                       const Rep2& v)
@@ -235,7 +237,7 @@ namespace units {
     return ret(ret(q).count() * v);
   }
 
-  template<typename Dimension, typename Rep1, typename Rep2, class Ratio>
+  template<typename Rep1, Dimension Dimension, typename Rep2, mp::Ratio Ratio>
   quantity<Dimension, std::common_type_t<Rep1, Rep2>, Ratio>
   constexpr operator*(const Rep1& v,
                       const quantity<Dimension, Rep2, Ratio>& q)
@@ -243,8 +245,8 @@ namespace units {
     return q * v;
   }
 
-  template<typename Dimension1, typename Rep1, class Ratio1, typename Dimension2, typename Rep2, class Ratio2,
-      mp::Requires<treat_as_floating_point_v<std::common_type_t<Rep1, Rep2>> || std::ratio_multiply<Ratio1, Ratio2>::den == 1> = true>
+  template<Dimension Dimension1, typename Rep1, mp::Ratio Ratio1, Dimension Dimension2, typename Rep2, mp::Ratio Ratio2>
+      requires treat_as_floating_point_v<std::common_type_t<Rep1, Rep2>> || std::ratio_multiply<Ratio1, Ratio2>::den == 1
   quantity<dimension_multiply_t<Dimension1, Dimension2>, std::common_type_t<Rep1, Rep2>, std::ratio_multiply<Ratio1, Ratio2>>
   constexpr operator*(const quantity<Dimension1, Rep1, Ratio1>& lhs,
                       const quantity<Dimension2, Rep2, Ratio2>& rhs)
@@ -253,7 +255,7 @@ namespace units {
     return ret(lhs.count() * rhs.count());
   }
 
-  template<typename Rep1, typename Exponent, class Ratio, typename Rep2>
+  template<typename Rep1, Exp Exponent, mp::Ratio Ratio, typename Rep2>
   quantity<dimension<exp_invert_t<Exponent>>, std::common_type_t<Rep1, Rep2>, Ratio>
   constexpr operator/(const Rep1& v,
                       const quantity<dimension<Exponent>, Rep2, Ratio>& q)
@@ -263,7 +265,7 @@ namespace units {
     return ret(v / den(q).count());
   }
 
-  template<typename Dimension, typename Rep1, class Ratio, typename Rep2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio, typename Rep2>
   quantity<Dimension, std::common_type_t<Rep1, Rep2>, Ratio>
   constexpr operator/(const quantity<Dimension, Rep1, Ratio>& q,
                       const Rep2& v)
@@ -272,7 +274,7 @@ namespace units {
     return ret(ret(q).count() / v);
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   std::common_type_t<Rep1, Rep2>
   constexpr operator/(const quantity<Dimension, Rep1, Ratio1>& lhs,
                       const quantity<Dimension, Rep2, Ratio2>& rhs)
@@ -281,8 +283,8 @@ namespace units {
     return cq(lhs).count() / cq(rhs).count();
   }
 
-  template<typename Dimension1, typename Rep1, class Ratio1, typename Dimension2, typename Rep2, class Ratio2,
-      mp::Requires<treat_as_floating_point_v<std::common_type_t<Rep1, Rep2>> || std::ratio_divide<Ratio1, Ratio2>::den == 1> = true>
+  template<Dimension Dimension1, typename Rep1, mp::Ratio Ratio1, Dimension Dimension2, typename Rep2, mp::Ratio Ratio2>
+      requires treat_as_floating_point_v<std::common_type_t<Rep1, Rep2>> || std::ratio_divide<Ratio1, Ratio2>::den == 1
   quantity<dimension_divide_t<Dimension1, Dimension2>, std::common_type_t<Rep1, Rep2>, std::ratio_divide<Ratio1, Ratio2>>
   constexpr operator/(const quantity<Dimension1, Rep1, Ratio1>& lhs,
                       const quantity<Dimension2, Rep2, Ratio2>& rhs)
@@ -291,7 +293,7 @@ namespace units {
     return ret(lhs.count() / rhs.count());
   }
 
-  template<typename Dimension, typename Rep1, class Ratio, typename Rep2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio, typename Rep2>
   quantity<Dimension, std::common_type_t<Rep1, Rep2>, Ratio>
   constexpr operator%(const quantity<Dimension, Rep1, Ratio>& q,
                       const Rep2& v)
@@ -300,7 +302,7 @@ namespace units {
     return ret(ret(q).count() % v);
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   std::common_type_t<quantity<Dimension, Rep1, Ratio1>, quantity<Dimension, Rep2, Ratio2>>
   constexpr operator%(const quantity<Dimension, Rep1, Ratio1>& lhs,
                       const quantity<Dimension, Rep2, Ratio2>& rhs)
@@ -309,7 +311,9 @@ namespace units {
     return ret(ret(lhs).count() % ret(rhs).count());
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  // clang-format on
+
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   constexpr bool operator==(const quantity<Dimension, Rep1, Ratio1>& lhs,
                             const quantity<Dimension, Rep2, Ratio2>& rhs)
   {
@@ -317,14 +321,14 @@ namespace units {
     return ct(lhs).count() == ct(rhs).count();
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   constexpr bool operator!=(const quantity<Dimension, Rep1, Ratio1>& lhs,
                             const quantity<Dimension, Rep2, Ratio2>& rhs)
   {
     return !(lhs == rhs);
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   constexpr bool operator<(const quantity<Dimension, Rep1, Ratio1>& lhs,
                            const quantity<Dimension, Rep2, Ratio2>& rhs)
   {
@@ -332,34 +336,33 @@ namespace units {
     return ct(lhs).count() < ct(rhs).count();
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   constexpr bool operator<=(const quantity<Dimension, Rep1, Ratio1>& lhs,
                             const quantity<Dimension, Rep2, Ratio2>& rhs)
   {
     return !(rhs < lhs);
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   constexpr bool operator>(const quantity<Dimension, Rep1, Ratio1>& lhs,
                            const quantity<Dimension, Rep2, Ratio2>& rhs)
   {
     return rhs < lhs;
   }
 
-  template<typename Dimension, typename Rep1, class Ratio1, typename Rep2, class Ratio2>
+  template<Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   constexpr bool operator>=(const quantity<Dimension, Rep1, Ratio1>& lhs,
                             const quantity<Dimension, Rep2, Ratio2>& rhs)
   {
     return !(lhs < rhs);
   }
-  // clang-format on
 
 }  // namespace units
 
 namespace std {
 
   // todo: simplified
-  template<typename Dimension, typename Rep1, typename Ratio1, typename Rep2, typename Ratio2>
+  template<units::Dimension Dimension, typename Rep1, mp::Ratio Ratio1, typename Rep2, mp::Ratio Ratio2>
   struct common_type<units::quantity<Dimension, Rep1, Ratio1>, units::quantity<Dimension, Rep2, Ratio2>> {
     using type =
         units::quantity<Dimension, std::common_type_t<Rep1, Rep2>, mp::common_ratio_t<Ratio1, Ratio2>>;

src/include/units/si/base_dimensions.h

@@ -23,7 +23,6 @@
 #pragma once
 
 #include "../dimension.h"
-#include "../quantity.h"
 
 namespace units {
 

src/include/units/si/length.h

@@ -23,6 +23,7 @@
 #pragma once
 
 #include "base_dimensions.h"
+#include "../quantity.h"
 
 namespace units {
 

src/include/units/si/time.h

@@ -23,6 +23,7 @@
 #pragma once
 
 #include "base_dimensions.h"
+#include "../quantity.h"
 
 namespace units {