From c06a533f500d3a8456b2972fdfcbd71a897a9a15 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Fri, 6 Sep 2024 18:30:58 +0200
Subject: [PATCH] refactor: `Representation` concepts now requires
 `WeaklyRegular` instead of `std::regular`

---
 .../include/mp-units/framework/representation_concepts.h    | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/core/include/mp-units/framework/representation_concepts.h b/src/core/include/mp-units/framework/representation_concepts.h
index 6019d215..5adbbee0 100644
--- a/src/core/include/mp-units/framework/representation_concepts.h
+++ b/src/core/include/mp-units/framework/representation_concepts.h
@@ -79,10 +79,14 @@ concept Scalable =
   CastableNumber<T> || (requires { typename wrapped_type_t<T>; } && CastableNumber<wrapped_type_t<T>> &&
                         ScalableNumber<T, std::common_type_t<wrapped_type_t<T>, std::intmax_t>>);
 
+template<typename T>
+concept WeaklyRegular = std::copyable<T> && std::equality_comparable<T>;
+
 }  // namespace detail
 
 MP_UNITS_EXPORT template<typename T>
-concept Representation = (is_scalar<T> || is_vector<T> || is_tensor<T>)&&std::regular<T> && detail::Scalable<T>;
+concept Representation =
+  (is_scalar<T> || is_vector<T> || is_tensor<T>)&&detail::WeaklyRegular<T> && detail::Scalable<T>;
 
 MP_UNITS_EXPORT template<typename T, quantity_character Ch>
 concept RepresentationOf = Representation<T> && ((Ch == quantity_character::scalar && is_scalar<T>) ||