Actually, C++ does limit the non-type template parameters[0] to integral types, enums and function pointers. But some people have found that too restrictive and

Actually, C++ does limit the non-type template parameters[0] to integral types, enums and function pointers. But some people have found that too restrictive and would like to use other constants as well, like string literals. [0]: https://en.cppreference.com/w/cpp/language/template_parameters#Non-type_template_parameter https://en.cppreference.com/w/cpp/language/template_paramete...