From 95028d10a72ff88afdd6123ebd527fac12ee0ff0 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Thu, 17 Oct 2019 18:22:51 +0200
Subject: [PATCH] gcc-10 enabled

---
 example/example.cpp               |  4 ++--
 src/CMakeLists.txt                |  7 ++++++-
 src/include/units/bits/concepts.h | 26 ++++++++++++++++++++++++++
 src/include/units/bits/hacks.h    |  6 ++++++
 src/include/units/math.h          |  4 ++--
 src/include/units/quantity.h      | 24 ++++++++++++------------
 6 files changed, 54 insertions(+), 17 deletions(-)

diff --git a/example/example.cpp b/example/example.cpp
index a4424a7d..c5c1b03d 100644
--- a/example/example.cpp
+++ b/example/example.cpp
@@ -28,7 +28,7 @@ namespace {
 using namespace units::literals;
 
 template<units::Length D, units::Time T>
-constexpr units::Velocity avg_speed(D d, T t)
+constexpr units::Velocity AUTO avg_speed(D d, T t)
 {
   return d / t;
 }
@@ -36,7 +36,7 @@ constexpr units::Velocity avg_speed(D d, T t)
 template<units::Velocity V, units::Time T>
 void example_1(V v, T t)
 {
-  const units::Length distance = v * t;
+  const units::Length AUTO distance = v * t;
   std::cout << "A car driving " << v.count() << " km/h in a time of " << t.count() << " minutes will pass "
             << units::quantity_cast<units::quantity<units::metre, double>>(distance).count() << " metres.\n";
 }
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4c04161c..09c9c3bb 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -63,12 +63,17 @@ target_include_directories(units
 if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
     target_compile_options(units
         INTERFACE
-            -fconcepts
             -Wno-literal-suffix
             -Wno-non-template-friend
 # TODO gcc:92101
             -Wno-pedantic
     )
+    if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10.0)
+        target_compile_options(units
+            INTERFACE
+                -fconcepts
+        )
+    endif()
 endif()
 add_library(mp::units ALIAS units)
 
diff --git a/src/include/units/bits/concepts.h b/src/include/units/bits/concepts.h
index aaba6331..bf41edc4 100644
--- a/src/include/units/bits/concepts.h
+++ b/src/include/units/bits/concepts.h
@@ -26,6 +26,8 @@
 
 namespace units {
 
+#if __GNUC__ < 10
+
   template<typename T>
   concept Number = std::regular<T> &&
       std::totally_ordered<T> &&
@@ -44,4 +46,28 @@ namespace units {
         // …
   };
 
+#else
+
+  template<typename T>
+  concept Number = std::regular<T> &&
+      std::totally_ordered<T> &&
+      requires(T a, T b) {
+        { a + b } -> std::same_as<T>;
+        { a - b } -> std::same_as<T>;
+        { a * b } -> std::same_as<T>;
+        { a / b } -> std::same_as<T>;
+        { +a } -> std::same_as<T>;
+        { -a } -> std::same_as<T>;
+        { a += b } -> std::same_as<T&>;
+        { a -= b } -> std::same_as<T&>;
+        { a *= b } -> std::same_as<T&>;
+        { a /= b } -> std::same_as<T&>;
+        { T{0} };    // can construct a T from a zero
+        // …
+  };
+
+#endif
+
+  // InstanceOf
+
 }  // namespace units
diff --git a/src/include/units/bits/hacks.h b/src/include/units/bits/hacks.h
index 31ed51bd..a587601b 100644
--- a/src/include/units/bits/hacks.h
+++ b/src/include/units/bits/hacks.h
@@ -31,6 +31,12 @@
 #define Expects(cond) assert(cond);
 #endif
 
+#if __GNUC__ > 9
+#define AUTO auto
+#else
+#define AUTO
+#endif
+
 namespace std {
 
   // concepts
diff --git a/src/include/units/math.h b/src/include/units/math.h
index 46628653..f9e0d289 100644
--- a/src/include/units/math.h
+++ b/src/include/units/math.h
@@ -28,7 +28,7 @@
 namespace units {
 
   template<std::size_t N, typename U, typename Rep>
-  inline Quantity pow(const quantity<U, Rep>& q) noexcept
+  inline Quantity AUTO pow(const quantity<U, Rep>& q) noexcept
   {
     using dim = dimension_pow<typename U::dimension, N>;
     using r = ratio_pow<typename U::ratio, N>;
@@ -36,7 +36,7 @@ namespace units {
   }
 
   template<typename U, typename Rep>
-  inline Quantity sqrt(const quantity<U, Rep>& q) noexcept
+  inline Quantity AUTO sqrt(const quantity<U, Rep>& q) noexcept
   {
     using dim = dimension_sqrt<typename U::dimension>;
     using r = ratio_sqrt<typename U::ratio>;
diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index ff2a86a9..380bd911 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -307,7 +307,7 @@ namespace units {
   };
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator+(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Quantity AUTO operator+(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
       requires same_dim<typename U1::dimension, typename U2::dimension>
   {
     using common_rep = decltype(lhs.count() + rhs.count());
@@ -316,7 +316,7 @@ namespace units {
   }
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator-(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Quantity AUTO operator-(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
       requires same_dim<typename U1::dimension, typename U2::dimension>
   {
     using common_rep = decltype(lhs.count() - rhs.count());
@@ -325,7 +325,7 @@ namespace units {
   }
 
   template<typename U, typename Rep1, Scalar Rep2>
-  [[nodiscard]] constexpr Quantity operator*(const quantity<U, Rep1>& q, const Rep2& v)
+  [[nodiscard]] constexpr Quantity AUTO operator*(const quantity<U, Rep1>& q, const Rep2& v)
       requires (!Quantity<Rep2>)
   {
     using common_rep = decltype(q.count() * v);
@@ -334,14 +334,14 @@ namespace units {
   }
 
   template<Scalar Rep1, typename U, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator*(const Rep1& v, const quantity<U, Rep2>& q)
+  [[nodiscard]] constexpr Quantity AUTO operator*(const Rep1& v, const quantity<U, Rep2>& q)
       requires (!Quantity<Rep1>)
   {
     return q * v;
   }
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Scalar operator*(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Scalar AUTO operator*(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
       requires same_dim<typename U1::dimension, dim_invert<typename U2::dimension>>
   {
     using common_rep = decltype(lhs.count() * rhs.count());
@@ -350,7 +350,7 @@ namespace units {
   }
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator*(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Quantity AUTO operator*(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
       requires (!same_dim<typename U1::dimension, dim_invert<typename U2::dimension>>) &&
               (treat_as_floating_point<decltype(lhs.count() * rhs.count())> ||
                 (std::ratio_multiply<typename U1::ratio, typename U2::ratio>::den == 1))
@@ -362,7 +362,7 @@ namespace units {
   }
 
   template<Scalar Rep1, typename U, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator/(const Rep1& v, const quantity<U, Rep2>& q)
+  [[nodiscard]] constexpr Quantity AUTO operator/(const Rep1& v, const quantity<U, Rep2>& q)
       requires (!Quantity<Rep1>)
   {
     Expects(q != std::remove_cvref_t<decltype(q)>(0));
@@ -375,7 +375,7 @@ namespace units {
   }
 
   template<typename U, typename Rep1, Scalar Rep2>
-  [[nodiscard]] constexpr Quantity operator/(const quantity<U, Rep1>& q, const Rep2& v)
+  [[nodiscard]] constexpr Quantity AUTO operator/(const quantity<U, Rep1>& q, const Rep2& v)
       requires (!Quantity<Rep2>)
   {
     Expects(v != Rep2{0});
@@ -386,7 +386,7 @@ namespace units {
   }
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Scalar operator/(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Scalar AUTO operator/(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
       requires same_dim<typename U1::dimension, typename U2::dimension>
   {
     Expects(rhs != std::remove_cvref_t<decltype(rhs)>(0));
@@ -397,7 +397,7 @@ namespace units {
   }
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator/(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Quantity AUTO operator/(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
       requires (!same_dim<typename U1::dimension, typename U2::dimension>) &&
               (treat_as_floating_point<decltype(lhs.count() / rhs.count())> ||
                 (ratio_divide<typename U1::ratio, typename U2::ratio>::den == 1))
@@ -411,7 +411,7 @@ namespace units {
   }
 
   template<typename U, typename Rep1, Scalar Rep2>
-  [[nodiscard]] constexpr Quantity operator%(const quantity<U, Rep1>& q, const Rep2& v)
+  [[nodiscard]] constexpr Quantity AUTO operator%(const quantity<U, Rep1>& q, const Rep2& v)
   {
     using common_rep = decltype(q.count() % v);
     using ret = quantity<U, common_rep>;
@@ -419,7 +419,7 @@ namespace units {
   }
 
   template<typename U1, typename Rep1, typename U2, typename Rep2>
-  [[nodiscard]] constexpr Quantity operator%(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
+  [[nodiscard]] constexpr Quantity AUTO operator%(const quantity<U1, Rep1>& lhs, const quantity<U2, Rep2>& rhs)
   {
     using common_rep = decltype(lhs.count() % rhs.count());
     using ret = common_quantity<quantity<U1, Rep1>, quantity<U2, Rep2>, common_rep>;