code: private LNGIntVector generateClauseVector(final Formula clause) {
          final LNGIntVector clauseVec = new LNGIntVector(clause.numberOfOperands());
          for (final Literal lit : clause.literals()) {
              int index = this.idxForName(lit.name());
              if (index == -1) {
                  index = this.newVar(false, true);
                  this.addName(lit.name(), index);
              }
              final int litNum = lit.phase() ? index * 2 : (index * 2) ^ 1;
              clauseVec.push(litNum);
          }
          return clauseVec;
      }
docs: Generates a solver vector of a clause.
  @param clause the clause
  @return the solver vector