@Override
    public String toString() {
        StringBuffer buf = new StringBuffer(disjuncts.get(0).toString());
        for(int i=1;i<disjuncts.size();i++) {
            buf.append("|");
            String as = disjuncts.get(i).toString();
            if(as.startsWith("(") && as.endsWith(")"))
                as = as .substring(1,as.length()-1);
            buf.append(as);
        }
        return "(" + buf + ")";
    }