fix: missing get_common_unit() overload added

Resolves #666
mpusz · Jan 21, 2025 · becb456 · becb456
1 parent a489548
commit becb456
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diff --git a/src/core/include/mp-units/framework/unit.h b/src/core/include/mp-units/framework/unit.h
@@ -750,6 +750,16 @@ template<Unit... Us, Unit NewUnit>
   return get_common_unit(cu, nu);
 }
 
+template<Unit Front, Unit... Rest, Unit... Us>
+  requires(interconvertible(common_unit<Front, Rest...>{}, common_unit<Us...>{}))
+[[nodiscard]] consteval Unit auto get_common_unit(common_unit<Front, Rest...>, common_unit<Us...>)
+{
+  if constexpr (sizeof...(Rest) == 1)
+    return get_common_unit(Front{}, get_common_unit(Rest{}..., common_unit<Us...>{}));
+  else
+    return get_common_unit(Front{}, get_common_unit(common_unit<Rest...>{}, common_unit<Us...>{}));
+}
+
 [[nodiscard]] consteval Unit auto get_common_unit(Unit auto u1, Unit auto u2, Unit auto u3, Unit auto... rest)
   requires requires { get_common_unit(get_common_unit(u1, u2), u3, rest...); }
 {

diff --git a/test/static/unit_test.cpp b/test/static/unit_test.cpp
@@ -67,6 +67,7 @@ inline constexpr struct pascal_ final : named_unit<"Pa", newton / square(metre)>
 inline constexpr struct joule_ final : named_unit<"J", newton * metre> {} joule;
 inline constexpr struct watt_ final : named_unit<"W", joule / second> {} watt;
 inline constexpr struct degree_Celsius_ final : named_unit<symbol_text{u8"℃", "`C"}, kelvin> {} degree_Celsius;
+inline constexpr struct degree_Fahrenheit_ final : named_unit<symbol_text{u8"℉", "`F"}, mag_ratio<5, 9> * degree_Celsius> {} degree_Fahrenheit;
 
 inline constexpr struct minute_ final : named_unit<"min", mag<60> * second> {} minute;
 inline constexpr struct hour_ final : named_unit<"h", mag<60> * minute> {} hour;
@@ -568,6 +569,11 @@ static_assert(is_of_type<get_common_unit(kilometre / hour, metre / second),
 static_assert(is_of_type<get_common_unit(metre / second, kilometre / hour),
                          common_unit<decltype(kilometre / hour), decltype(metre / second)>>);
 static_assert(is_of_type<get_common_unit(radian, degree), common_unit<degree_, radian_>>);
+static_assert(
+  is_of_type<get_common_unit(degree_Celsius, degree_Fahrenheit), common_unit<degree_Celsius_, degree_Fahrenheit_>>);
+static_assert(is_of_type<get_common_unit(get_common_unit(degree_Celsius, degree_Fahrenheit),
+                                         get_common_unit(mag_ratio<5, 9>* degree_Celsius, si::milli<kelvin>)),
+                         common_unit<degree_Fahrenheit_, si::milli_<kelvin_>>>);
 
 static_assert(
   is_of_type<get_common_unit(mile, kilometre) / second, derived_unit<common_unit<kilo_<metre_>, mile_>, per<second_>>>);