Check c++20 feature __cpp_lib_ranges

src/varray.h

@@ -15,7 +15,11 @@
 #include <cassert>
 #include "compare.h"
 
+#ifdef __cpp_lib_ranges
 namespace ranges = std::ranges;
+#else
+#error C++20 Ranges library is Not Available!
+#endif
 
 // unary operators
 // clang-format off