D.R.Y. people should love macro lists

macro_list_example.cc

// Seems like anyone who follows the "Don't Repeat Yourself" principle 
// should be into macro lists

#define COMMANDS(OP) \
  OP(Jump)     \
  OP(Call)     \
  OP(Return)   \
  OP(Noop)     \
  OP(Add)      \
  
// Make enum
#define COMMAND_OP(name) name,

enum CommandId 
{
  Commands(MAKE_ENUM)
  
  LAST_COMMAND,
};

#undef COMMAND_OP


// For debugging, make a command to string function.
const char* GetCommandString(CommandId command) 
{
  #define COMMAND_OP(name) #name,
  static const char* command_names[] = {
    COMMANDS(COMMAND_OP)
  };
  #undef COMMAND_OP
  return (command >= 0 && command < LAST_COMMAND) 
     ? command_names[command]
     : "**unknown command**"
}

typedef bool (*CommandFn)(ExecutionContext*);

// pre-declare functions
#define COMMAND_OP(name) \
    extern bool Handle ## name(E)(ExecutionContext* ec);
COMMANDS(COMMAND_OP)
#undef COMMAND_OP

bool ProcessCommand(CommandId command, ExecutionContext* ec) 
{
  // Make jump table
  #define COMMAND_OP(name)   Handle ## name,
  static CommandFn command_jump_table[] = 
  {
      COMMANDS(COMMAND_OP)
  };
  #undef COMMAND_OP

  if (g_debug) 
  {
    Logf("%s\n", GetCommandString(command));
  }
  ASSERT(command >= 0 && command < LAST_COMMAND);
  return command_jump_table[command](ec);
}
  
// Now all you need to do is implement each command.
// Adding a command you only have to edit 1 place, the 
// COMMANDS macro and then add a function 'HandleNameOfCommand'
// where as without the COMMANDS macro you'd have to repeat
// yourself in 4 places.