refactor: expr_fractions takes direct OneType type now instead of a trait

src/core/include/mp-units/framework/dimension.h

@@ -59,9 +59,6 @@ MP_UNITS_EXPORT struct dimension_one;
 
 namespace detail {
 
-template<typename T>
-struct is_dimension_one : std::false_type {};
-
 template<typename Lhs, typename Rhs>
 struct base_dimension_less : std::bool_constant<type_name<Lhs>() < type_name<Rhs>()> {};
 
@@ -69,7 +66,7 @@ template<typename T1, typename T2>
 using type_list_of_base_dimension_less = expr_less<T1, T2, base_dimension_less>;
 
 template<typename... Expr>
-struct derived_dimension_impl : expr_fractions<is_dimension_one, Expr...> {};
+struct derived_dimension_impl : expr_fractions<dimension_one, Expr...> {};
 
 struct dimension_interface {
   template<Dimension Lhs, Dimension Rhs>
@@ -183,13 +180,6 @@ MP_UNITS_EXPORT inline constexpr struct dimension_one final :
     detail::derived_dimension_impl<> {
 } dimension_one;
 
-namespace detail {
-
-template<>
-struct is_dimension_one<struct dimension_one> : std::true_type {};
-
-}  // namespace detail
-
 MP_UNITS_EXPORT_BEGIN
 
 [[nodiscard]] consteval Dimension auto inverse(Dimension auto d) { return dimension_one / d; }

src/core/include/mp-units/framework/expression_template.h

@@ -294,7 +294,7 @@ struct expr_fractions_result {
   using _den_ = Den;  // exposition only
 };
 
-template<template<typename> typename OneType, typename List>
+template<typename OneType, typename List>
 [[nodiscard]] consteval auto expr_fractions_impl()
 {
   constexpr std::size_t size = type_list_size<List>;
@@ -307,7 +307,7 @@ template<template<typename> typename OneType, typename List>
     using last_element = type_list_back<List>;
 
     if constexpr (is_specialization_of<last_element, per>) {
-      if constexpr (size == 2 && OneType<type_list_front<List>>::value)
+      if constexpr (size == 2 && is_same_v<type_list_front<List>, OneType>)
         return expr_fractions_result<type_list<>, type_list_map<last_element, type_list>>{};
       else {
         using split = type_list_split<List, size - 1>;
@@ -322,7 +322,7 @@ template<template<typename> typename OneType, typename List>
 /**
  * @brief Divides expression template spec to numerator and denominator parts
  */
-template<template<typename> typename OneType, typename... Ts>
+template<typename OneType, typename... Ts>
 struct expr_fractions : decltype(expr_fractions_impl<OneType, type_list<Ts...>>()) {};
 
 // expr_make_spec

src/core/include/mp-units/framework/quantity_spec.h

@@ -429,9 +429,6 @@ struct quantity_spec<Self, QS, Eq, Args...> : detail::quantity_spec_interface<Se
 
 namespace detail {
 
-template<typename T>
-struct is_dimensionless : std::false_type {};
-
 template<typename... Expr>
 struct derived_quantity_spec_impl :
 #if MP_UNITS_API_NO_CRTP
@@ -439,9 +436,9 @@ struct derived_quantity_spec_impl :
 #else
     detail::quantity_spec_interface<derived_quantity_spec<Expr...>>,
 #endif
-    detail::expr_fractions<detail::is_dimensionless, Expr...> {
+    detail::expr_fractions<dimensionless, Expr...> {
   using _base_type_ = derived_quantity_spec_impl;
-  using _base_ = detail::expr_fractions<detail::is_dimensionless, Expr...>;
+  using _base_ = detail::expr_fractions<dimensionless, Expr...>;
 
   static constexpr Dimension auto dimension =
     detail::expr_map<detail::to_dimension, derived_dimension, struct dimension_one,
@@ -506,13 +503,6 @@ struct derived_quantity_spec final : detail::derived_quantity_spec_impl<Expr...>
  */
 MP_UNITS_EXPORT QUANTITY_SPEC(dimensionless, derived_quantity_spec<>{});
 
-namespace detail {
-
-template<>
-struct is_dimensionless<struct dimensionless> : std::true_type {};
-
-}  // namespace detail
-
 /**
  * @brief Quantity kind specifier
  *

src/core/include/mp-units/framework/unit.h

@@ -461,11 +461,8 @@ struct common_unit final : decltype(detail::get_common_scaled_unit(U1{}, U2{}, R
 
 namespace detail {
 
-template<typename T>
-struct is_one : std::false_type {};
-
 template<typename... Expr>
-struct derived_unit_impl : detail::unit_interface, detail::expr_fractions<detail::is_one, Expr...> {
+struct derived_unit_impl : detail::unit_interface, detail::expr_fractions<one, Expr...> {
   using _base_type_ = derived_unit_impl;  // exposition only
 };
 
@@ -530,9 +527,6 @@ MP_UNITS_EXPORT inline constexpr struct one final : detail::derived_unit_impl<>
 
 namespace detail {
 
-template<>
-struct is_one<struct one> : std::true_type {};
-
 template<Unit T, auto M, typename U>
 [[nodiscard]] consteval auto get_canonical_unit_impl(T, const scaled_unit_impl<M, U>&)
 {