libstdc++: Define and use variable templates in <chrono>

[gcc.git] / libstdc++-v3 / include / bits / chrono.h

diff --git a/libstdc++-v3/include/bits/chrono.h b/libstdc++-v3/include/bits/chrono.h
index 22c0be3fbe6de4b7eba35366011005f5bc0ed662..56751d1c3a0fb4e096f975e34f1fd5b9f75357e6 100644 (file)
--- a/libstdc++-v3/include/bits/chrono.h
+++ b/libstdc++-v3/include/bits/chrono.h
@@ -244,6 +244,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       using __disable_if_is_duration
        = typename enable_if<!__is_duration<_Tp>::value, _Tp>::type;
 
+#if __cpp_variable_templates
+    template<typename _Tp>
+      inline constexpr bool __is_duration_v = false;
+    template<typename _Rep, typename _Period>
+      inline constexpr bool __is_duration_v<duration<_Rep, _Period>> = true;
+    template<typename _Tp>
+      inline constexpr bool __is_time_point_v = false;
+    template<typename _Clock, typename _Dur>
+      inline constexpr bool __is_time_point_v<time_point<_Clock, _Dur>> = true;
+#endif
+
     /// @endcond
 
     /** Convert a `duration` to type `ToDur`.
@@ -261,13 +272,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr __enable_if_is_duration<_ToDur>
       duration_cast(const duration<_Rep, _Period>& __d)
       {
-       typedef typename _ToDur::period                         __to_period;
-       typedef typename _ToDur::rep                            __to_rep;
-       typedef ratio_divide<_Period, __to_period>              __cf;
-       typedef typename common_type<__to_rep, _Rep, intmax_t>::type __cr;
-       typedef  __duration_cast_impl<_ToDur, __cf, __cr,
-                                     __cf::num == 1, __cf::den == 1> __dc;
-       return __dc::__cast(__d);
+#if __cpp_inline_variables && __cpp_if_constexpr
+       if constexpr (is_same_v<_ToDur, duration<_Rep, _Period>>)
+         return __d;
+       else
+#endif
+       {
+         using __to_period = typename _ToDur::period;
+         using __to_rep = typename _ToDur::rep;
+         using __cf = ratio_divide<_Period, __to_period>;
+         using __cr = typename common_type<__to_rep, _Rep, intmax_t>::type;
+         using __dc = __duration_cast_impl<_ToDur, __cf, __cr,
+                                           __cf::num == 1, __cf::den == 1>;
+         return __dc::__cast(__d);
+       }
       }
 
     /** Trait indicating whether to treat a type as a floating-point type.
@@ -290,6 +308,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     template <typename _Rep>
       inline constexpr bool treat_as_floating_point_v =
        treat_as_floating_point<_Rep>::value;
+
+    template<>
+      inline constexpr bool treat_as_floating_point_v<int> = false;
+    template<>
+      inline constexpr bool treat_as_floating_point_v<long> = false;
+    template<>
+      inline constexpr bool treat_as_floating_point_v<long long> = false;
+    template<>
+      inline constexpr bool treat_as_floating_point_v<float> = true;
+    template<>
+      inline constexpr bool treat_as_floating_point_v<double> = true;
+    template<>
+      inline constexpr bool treat_as_floating_point_v<long double> = true;
 #endif // C++17
 
 #if __cplusplus > 201703L
@@ -632,8 +663,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        // DR 934.
        template<typename _Rep2 = rep>
          _GLIBCXX17_CONSTEXPR
-         typename enable_if<!treat_as_floating_point<_Rep2>::value,
-                            duration&>::type
+         __enable_if_t<!treat_as_floating_point<_Rep2>::value, duration&>
          operator%=(const rep& __rhs)
          {
            __r %= __rhs;
@@ -642,8 +672,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
        template<typename _Rep2 = rep>
          _GLIBCXX17_CONSTEXPR
-         typename enable_if<!treat_as_floating_point<_Rep2>::value,
-                            duration&>::type
+         __enable_if_t<!treat_as_floating_point<_Rep2>::value, duration&>
          operator%=(const duration& __d)
          {
            __r %= __d.count();
@@ -1019,7 +1048,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
      */
     template<typename _ToDur, typename _Clock, typename _Dur>
       [[nodiscard]] constexpr
-      enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
+      enable_if_t<__is_duration_v<_ToDur>, time_point<_Clock, _ToDur>>
       floor(const time_point<_Clock, _Dur>& __tp)
       {
        return time_point<_Clock, _ToDur>{
@@ -1040,7 +1069,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
      */
     template<typename _ToDur, typename _Clock, typename _Dur>
       [[nodiscard]] constexpr
-      enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
+      enable_if_t<__is_duration_v<_ToDur>, time_point<_Clock, _ToDur>>
       ceil(const time_point<_Clock, _Dur>& __tp)
       {
        return time_point<_Clock, _ToDur>{
@@ -1062,10 +1091,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
      */
     template<typename _ToDur, typename _Clock, typename _Dur>
       [[nodiscard]] constexpr
-      enable_if_t<
-       __and_<__is_duration<_ToDur>,
-              __not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
-       time_point<_Clock, _ToDur>>
+      enable_if_t<__is_duration_v<_ToDur>
+                   && !treat_as_floating_point_v<typename _ToDur::rep>,
+                 time_point<_Clock, _ToDur>>
       round(const time_point<_Clock, _Dur>& __tp)
       {
        return time_point<_Clock, _ToDur>{