Base dimensions refactored

-
2019-10-15 19:03:45 +02:00
parent c3c5a740d9
commit d31d2cf439
9 changed files with 108 additions and 68 deletions
@@ -24,31 +24,64 @@

 namespace units {

-//   TODO gcc:92101
-//   Gated by the following gcc bug
-//   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92101
-//
-//   template<typename CharT, std::size_t N>
-//   struct basic_fixed_string {
-//     CharT data_[N+1] = {};
+  template<typename CharT, std::size_t N>
+  struct basic_fixed_string {
+    CharT data_[N+1] = {};

-//     constexpr basic_fixed_string(const CharT (&txt)[N+1]) noexcept
-//     {
-//       for(std::size_t i = 0; i <= N; ++i)
-//         data_[i] = txt[i];
-//     }
-//     // auto operator==(const basic_fixed_string &) = default;
-//     [[nodiscard]] constexpr const CharT* c_str() const noexcept { return data_; }
-//   };
+    constexpr basic_fixed_string(const CharT (&txt)[N+1]) noexcept
+    {
+      for(std::size_t i = 0; i <= N; ++i)
+        data_[i] = txt[i];
+    }

-//   template<typename CharT, std::size_t N>
-//   basic_fixed_string(const CharT (&str)[N]) -> basic_fixed_string<CharT, N-1>;
+    [[nodiscard]] constexpr bool size() const noexcept { return N; }
+    [[nodiscard]] constexpr const CharT* c_str() const noexcept { return data_; }

-//   template<std::size_t N>
-//   using fixed_string = basic_fixed_string<char, N>;
+    // auto operator==(const basic_fixed_string &) = default;
+
+    [[nodiscard]] constexpr friend bool operator==(const basic_fixed_string& lhs, const basic_fixed_string& rhs) noexcept
+    {
+      for(size_t i = 0; i != size(lhs.data_); ++i)
+        if(lhs.name_[i] != rhs.data_[i])
+          return false;
+      return true;
+    }
+
+    template<typename CharT2, std::size_t N2>
+    [[nodiscard]] constexpr friend bool operator==(const basic_fixed_string&, const basic_fixed_string<CharT2, N2>&) noexcept
+    {
+      return false;
+    }
+
+    template<typename CharT2, std::size_t N2>
+    [[nodiscard]] constexpr friend bool operator<(const basic_fixed_string& lhs, const basic_fixed_string<CharT2, N2>& rhs) noexcept
+    {
+      using std::begin, std::end;
+      auto first1 = begin(lhs.data_);
+      auto first2 = begin(rhs.data_);
+      const auto last1 = std::prev(end(lhs.data_));  // do not waste time for '\0'
+      const auto last2 = std::prev(end(rhs.data_));
+
+      for(; (first1 != last1) && (first2 != last2); ++first1, (void)++first2 ) {
+        if(*first1 < *first2) return true;
+        if(*first2 < *first1) return false;
+      }
+      return first1 == last1 && first2 != last2;
+    }
+  };
+
+  template<typename CharT, std::size_t N>
+  basic_fixed_string(const CharT (&str)[N]) -> basic_fixed_string<CharT, N-1>;
+
+  template<std::size_t N>
+  using fixed_string = basic_fixed_string<char, N>;
+
+  // TODO gcc:92101
+  // hacked version to work with derived_unit
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92101

  template<typename CharT, CharT... Chars>
-  struct basic_fixed_string {
+  struct basic_fixed_string_hack {
    static constexpr CharT txt[] = { Chars..., '\0' };

    static constexpr const CharT* c_str() noexcept
@@ -60,7 +93,7 @@ namespace units {
  inline namespace hacks {

    template<typename T, T... chars>
-    constexpr basic_fixed_string<T, chars...> operator""_fs() { return {}; }
+    constexpr basic_fixed_string_hack<T, chars...> operator""_fs() { return {}; }

  }

@@ -24,37 +24,30 @@

 #include <units/bits/type_list.h>
 #include <units/bits/downcasting.h>
+#include <units/bits/fixed_string.h>
 #include <units/ratio.h>
 #include <ratio>

 namespace units {

+  template<basic_fixed_string Name, basic_fixed_string Symbol>
+  struct base_dimension {
+    static constexpr auto name = Name;
+    static constexpr auto symbol = Symbol;
+  };
+
  template<typename T>
  concept BaseDimension = std::is_empty_v<T> &&
      requires {
-        { T::value } -> std::same_as<const char*>;
-      };
-
-  namespace detail {
-
-    template<BaseDimension D1, BaseDimension D2>
-    constexpr bool less()
-    {
-      const char* p1 = D1::value;
-      const char* p2 = D2::value;
-      for(; (*p1 != '\0') && (*p2 != '\0'); ++p1, (void) ++p2) {
-        if(*p1 < *p2) return true;
-        if(*p2 < *p1) return false;
-      }
-      return (*p1 == '\0') && (*p2 != '\0');
-    }
-
-  }
+        T::name;
+        T::symbol;
+      };// &&  // TODO file a bug for this gcc issue
+//      std::derived_from<T, base_dimension<T::name, T::symbol>>;

  // base_dimension_less

  template<BaseDimension D1, BaseDimension D2>
-  struct base_dimension_less : std::bool_constant<detail::less<D1, D2>()> {
+  struct base_dimension_less : std::bool_constant<D1::name < D2::name> {
  };

  // is_exp
@@ -26,12 +26,12 @@

 namespace units {

-  struct base_dim_length { static constexpr const char* value = "length"; };
-  struct base_dim_mass { static constexpr const char* value = "mass"; };
-  struct base_dim_time { static constexpr const char* value = "time"; };
-  struct base_dim_current { static constexpr const char* value = "current"; };
-  struct base_dim_temperature { static constexpr const char* value = "temperature"; };
-  struct base_dim_substance { static constexpr const char* value = "substance"; };
-  struct base_dim_luminous_intensity { static constexpr const char* value = "luminous intensity"; };
+  struct base_dim_length : base_dimension<"length", "m"> {};
+  struct base_dim_mass : base_dimension<"mass", "kg"> {};
+  struct base_dim_time : base_dimension<"time", "s"> {};
+  struct base_dim_current : base_dimension<"current", "A"> {};
+  struct base_dim_temperature : base_dimension<"temperature", "K"> {};
+  struct base_dim_substance : base_dimension<"substance", "mol"> {};
+  struct base_dim_luminous_intensity : base_dimension<"luminous intensity", "cd"> {};

 }  // namespace units
@@ -24,7 +24,6 @@

 #include <units/dimension.h>
 #include <units/ratio.h>
-#include <units/bits/fixed_string.h>
 #include <ratio>

 namespace units {