code: private boolean isDNFClause(final Formula formula) {
      switch (formula.type()) {
        case TRUE:
        case FALSE:
        case LITERAL:
          return true;
        case IMPL:
        case EQUIV:
        case PBC:
        case NOT:
        case OR:
          return false;
        case AND:
          for (final Formula op : formula)
            if (op.type() != FType.LITERAL)
              return false;
          return true;
        default:
          throw new IllegalArgumentException("Cannot compute DNF clause predicate on " + formula.type());
      }
    }
docs: Returns {@code true} if the given formula is a DNF minterm, {@code false} otherwise.
  @param formula the formula
  @return {@code true} if the given formula is a DNF minterm