Function is_digit

example/cacheHierarchy/fkYAML/node.hpp:6034–6036

@brief Check if the given character is a digit. @note This function is needed to avoid assertion failures in `std::isdigit()` especially when compiled with MSVC. @param c A character to be checked. @return true if the given character is a digit, false otherwise.

    /// @param c A character to be checked.
    /// @return true if the given character is a digit, false otherwise.
    static bool is_digit(char c) {
        return ('0' <= c && c <= '9');
    }

    /// @brief Check if the given character is a hex-digit.
    /// @note This function is needed to avoid assertion failures in `std::isxdigit()` especially when compiled with