case ATerm.LIST: type = "<list>"; break;
  private ATermAppl normalize(ATermAppl appl)  {    ATermList args = appl.getArguments();    if (!args.isEmpty()) {      int len = args.getLength();      ATerm[] newargs = new ATerm[len];      String type = null;      for (int i=0; i<len; i++) {	ATerm arg = args.getFirst();	args = args.getNext();	switch (arg.getType()) {	  case ATerm.APPL:	    type = "<term>";	    break;	  case ATerm.LIST:	    type = "<list>";	    break;	  case ATerm.INT:	    type = "<int>";	    break;	  case ATerm.REAL:	    type = "<real>";	    break;	  case ATerm.PLACEHOLDER:	    newargs[i] = arg;	    break;	}	if (newargs[i] == null) {	  newargs[i] = factory.parse(type);	}      }      args = factory.makeList();      for (int i = len-1; i >= 0; i--) {	args = factory.makeList(newargs[i], args);      }    }    return factory.makeAppl(appl.getAFun(), args);      }