cleanup max and min in Math

amdis/common/Math.hpp

@@ -43,8 +43,8 @@ namespace AMDiS
     template <class T0, class T1>
     constexpr auto min(T0 a, T1 b)
     {
-      using T = std::conditional_t<(sizeof(T0)>sizeof(T1)),T0,T1>;
-      return a < b ? T(a) : T(b);
+      using T = std::common_type_t<T0,T1>;
+      return T(a) < T(b) ? a : b;
     }
 
     template <class T0>
@@ -69,8 +69,8 @@ namespace AMDiS
     template <class T0, class T1>
     constexpr auto max(T0 a, T1 b)
     {
-      using T = std::conditional_t<(sizeof(T0)>sizeof(T1)),T0,T1>;
-      return a < b ? T(b) : T(a);
+      using T = std::common_type_t<T0,T1>;
+      return T(a) < T(b) ? b : a;
     }
 
     template <class T0>