code: public void composeRightLeft(IntBitRelation left, IntBitRelation right) {
          int i, ele;
          IntBitSet li;
  
          for (i = 0; i < left.line.length; i++) {
              li = left.line[i];
              if (li != null) {
                  for (ele = li.first(); ele != -1; ele = li.next(ele)) {
                      if (right.line[ele] != null) {
                          add(i, right.line[ele]);
                      }
                  }
              }
          }
      }
docs: If (a,b) is element of left and (b,c) is element of right,
  then (a,c) is added to this relation.
  @param  left  left relation
  @param  right right relation.