code: private void extend() {
          while (!this.extension.empty()) {
              final int lit = this.extension.back();
              int other;
              boolean satisfied = false;
              while ((other = this.extension.back()) != 0) {
                  this.extension.pop();
                  if (val(other) == VALUE_TRUE) { satisfied = true; }
              }
              this.extension.pop();
              if (!satisfied) { this.vals.set(Math.abs(lit), sign(lit)); }
          }
      }
docs: Extends a partial to a full assignment.