add: eci_impl_check_handle(eci_rep);
context: void eci_command_float_arg_r(eci_handle_t ptr, const char* command, double arg){  struct eci_internal* eci_rep = (struct eci_internal*)ptr;  /* FIXME:    *  - send command to the ecasound instance   *  - read the return value and recognize its type   */  snprintf(eci_rep->farg_buf_repp, ECI_MAX_FLOAT_BUF_SIZE-1, "%s %.32f", command, arg);  eci_command_r(ptr, eci_rep->farg_buf_repp);}