/** The number of clauses so far. */
private int clauses = 0;
/** Helper method that returns a factory for WriteCNF instances. */
public static final SATFactory factory(final String filename) {
return new SATFactory() {
/** {@inheritDoc} */
@Override public SATSolver instance() { return new WriteCNF(filename); }
/** {@inheritDoc} */
@Override public boolean incremental() { return false; }
};