No Multiple Inheritance (Only Interface-Class Contracts): Code Examples

// C++: multiple inheritance of implementation
class Logger {
public:
  void log(const std::string& msg) { /* write log */ }
};

class Serializer {
public:
  std::string serialize() const { return "{}"; }
};

class Packet : public Logger, public Serializer {
public:
  int id;
};

// SystemVerilog: one extends chain + interface classes + composition
interface class loggable_if;
  pure virtual function void log(string msg);
endclass

interface class serializable_if;
  pure virtual function string serialize();
endclass

class logger_helper;
  function void write(string who, string msg);
    $display("[%0s] %0s", who, msg);
  endfunction
endclass

class packet extends uvm_sequence_item implements loggable_if, serializable_if;
  int id;
  logger_helper logger;

  function new(string name = "packet");
    super.new(name);
    logger = new();
  endfunction

  virtual function void log(string msg);
    logger.write(get_name(), msg);
  endfunction

  virtual function string serialize();
    return $sformatf("{id:%0d}", id);
  endfunction
endclass

// Java: one class inheritance + multiple interfaces with defaults
interface Auditable {
  default void audit(String m) { System.out.println("AUDIT " + m); }
}

interface JsonRenderable {
  String toJson();
}

class Event extends BaseEvent implements Auditable, JsonRenderable {
  int id;
  public String toJson() { return "{\"id\":" + id + "}"; }
}

// SystemVerilog: interfaces define contract only; helper owns implementation
interface class auditable_if;
  pure virtual function void audit(string m);
endclass

class audit_helper;
  function void do_audit(string m);
    $display("AUDIT %0s", m);
  endfunction
endclass

class event extends base_event implements auditable_if;
  int id;
  audit_helper ah;

  function new(string name = "event");
    super.new(name);
    ah = new();
  endfunction

  virtual function void audit(string m);
    ah.do_audit(m);
  endfunction

  function string to_json();
    return $sformatf("{\"id\":%0d}", id);
  endfunction
endclass