From 110a56dc3072c784142a2f4914d65844828a04f8 Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Mon, 28 Apr 2025 15:23:36 +0200
Subject: [PATCH] feat: `is_value_preserving` customization point added

---
 .../mp-units/framework/customization_points.h       | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/core/include/mp-units/framework/customization_points.h b/src/core/include/mp-units/framework/customization_points.h
index 430f7b9e..23bf4be7 100644
--- a/src/core/include/mp-units/framework/customization_points.h
+++ b/src/core/include/mp-units/framework/customization_points.h
@@ -60,6 +60,19 @@ constexpr bool treat_as_floating_point =
   std::is_floating_point_v<value_type_t<Rep>>;
 #endif
 
+/**
+ * @brief Specifies if a specific conversion between two types preserves the value
+ *
+ * This type trait should be specialized for a custom representation types to specify
+ * weather the conversion from the source type to the destination type preserves the value
+ * or not. Value-truncating conversions should be forced by the user with explicit casts.
+ *
+ * @tparam From a source representation type
+ * @tparam To a destination representation type
+ */
+template<typename From, typename To>
+constexpr bool is_value_preserving = treat_as_floating_point<To> || !treat_as_floating_point<From>;
+
 template<typename Rep>
 [[deprecated("2.5.0: `is_scalar` is no longer necessary and can simply be removed")]]
 constexpr bool is_scalar = false;