private int R()
{
int r_id;
if (cur_token != 'r' && cur_token != 'R')
error("错误的指令,寄存器标记必须以'R'开始,后跟0-31的数字");
get_src_token();
string n_w = get_number_word();
r_id = parse_number_16(n_w);
if (r_id < 0 || r_id > 31)
error("寄存器只能是从0到31");
//push_convert('R' + r_id.ToString() + ' ');
#if debug
Debug("get r" + r_id.ToString());
#endif
return r_id;
}