public APSet getAPs() { APSet rv; switch (kind) { case NOT: case NEXT: case GLOBALLY: case FINALLY: rv = left.getAPs(); break; case OR: case AND: case EQUIV: case IMPLIES: case UNTIL: case RELEASE: rv = left.getAPs(); for (String s : right.getAPs()) rv.addAP(s); break; // terminals case FALSE: case TRUE: rv = new APSet(); break; case AP: rv = new APSet(); rv.addAP(ap); break; default: rv = new APSet(); break; } return rv; }