void add_op(op_rec *op)
{
	switch (next_token()) {
	case PLUSOP:
	/* <add op>		-> PLUSOP #process_op */
		match(PLUSOP);
		*op = process_op();
		break;
	
	case MINUSOP:
	/* <add op>		-> MINUSOP #process_op */
		match(MINUSOP);
		*op = process_op();
		break;

	default:
		syntax_error(next_token());
	}
}