static int unoptag(Token token) {
        switch (token) {
        case PLUS:
            return JCTree.POS;
        case SUB:
            return JCTree.NEG;
        case BANG:
            return JCTree.NOT;
        case TILDE:
            return JCTree.COMPL;
        case PLUSPLUS:
            return JCTree.PREINC;
        case SUBSUB:
            return JCTree.PREDEC;
        default:
            return -1;
        }
    }