diff --git a/examples/range_pipe.cc b/examples/range_pipe.cc
index ad0f82f..4394055 100644
--- a/examples/range_pipe.cc
+++ b/examples/range_pipe.cc
@@ -73,7 +73,7 @@ int main() {
     /* more complex pipe */
     writeln("several piped algorithms");
 
-    srand(static_cast<unsigned int>(time(0)));
+    srand(static_cast<unsigned int>(std::time(nullptr)));
     std::array<int, 100> arr;
     generate(iter(arr), []() { return rand() % 128; });
 
diff --git a/ostd/range.hh b/ostd/range.hh
index e9a4ea4..c7070c6 100644
--- a/ostd/range.hh
+++ b/ostd/range.hh
@@ -177,17 +177,16 @@ struct contiguous_range_tag: finite_random_access_range_tag {};
 
 namespace detail {
     template<typename R>
-    struct range_category_test {
-        template<typename RR>
-        static char test(typename RR::range_category *);
-        template<typename>
-        static int test(...);
-        static constexpr bool value = (sizeof(test<R>(0)) == sizeof(char));
-    };
+    inline auto range_category_test(int) -> std::integral_constant<
+        bool, !std::is_void_v<typename R::range_category>
+    >;
+
+    template<typename>
+    inline std::false_type range_category_test(...);
 
     template<typename R>
     static inline constexpr bool const test_range_category =
-        range_category_test<R>::value;
+        decltype(range_category_test<R>(0))::value;
 
     template<typename R, bool, bool>
     struct range_traits_base {