From ada3c60ee9f6db71aa40828738a6301d2da77b98 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Tue, 16 Feb 2021 19:18:14 +0100
Subject: [PATCH] refactor: QuantityLike concept improved

---
 src/include/units/bits/basic_concepts.h | 26 +++++++++++++++++++------
 test/unit_test/static/chrono_test.cpp   |  1 +
 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/include/units/bits/basic_concepts.h b/src/include/units/bits/basic_concepts.h
index 50456c84..a6cb8569 100644
--- a/src/include/units/bits/basic_concepts.h
+++ b/src/include/units/bits/basic_concepts.h
@@ -261,6 +261,9 @@ inline constexpr bool is_quantity_kind = false;
 template<typename T>
 inline constexpr bool is_quantity_point_kind = false;
 
+template<typename T>
+inline constexpr bool is_quantity_like = false;
+
 }  // namespace detail
 
 /**
@@ -304,12 +307,7 @@ concept QuantityPointKind = detail::is_quantity_point_kind<T>;
  * type trait is provided.
  */
 template<typename T>
-concept QuantityLike = requires(T q) {
-  typename quantity_like_traits<T>::dimension;
-  typename quantity_like_traits<T>::unit;
-  typename quantity_like_traits<T>::rep;
-  { quantity_like_traits<T>::count(q) } -> std::convertible_to<typename quantity_like_traits<T>::rep>;
-};
+concept QuantityLike = detail::is_quantity_like<T>;
 
 // QuantityValue
 
@@ -378,4 +376,20 @@ concept QuantityValue =
   std::regular<T> &&
   scalable_<T>;
 
+namespace detail {
+
+template<typename T>
+  requires requires(T q) {
+    typename quantity_like_traits<T>::dimension;
+    typename quantity_like_traits<T>::unit;
+    typename quantity_like_traits<T>::rep;
+    requires Dimension<typename quantity_like_traits<T>::dimension>;
+    requires Unit<typename quantity_like_traits<T>::unit>;
+    requires QuantityValue<typename quantity_like_traits<T>::rep>;
+    { quantity_like_traits<T>::count(q) } -> std::convertible_to<typename quantity_like_traits<T>::rep>;
+  }
+inline constexpr bool is_quantity_like<T> = true;
+
+} // namespace detail
+
 }  // namespace units
diff --git a/test/unit_test/static/chrono_test.cpp b/test/unit_test/static/chrono_test.cpp
index 75fd86f6..61d80d3f 100644
--- a/test/unit_test/static/chrono_test.cpp
+++ b/test/unit_test/static/chrono_test.cpp
@@ -31,6 +31,7 @@ using namespace units::physical;
 using namespace units::physical::si::literals;
 using namespace std::chrono_literals;
 
+static_assert(QuantityLike<std::chrono::seconds>);
 
 // construction - same rep type
 static_assert(std::constructible_from<si::time<si::second, std::chrono::seconds::rep>, std::chrono::seconds>);