code: public char getSegmentStandin(int seg) {
          if (segmentStandins.length() < seg) {
              segmentStandins.setLength(seg);
          }
          char c = segmentStandins.charAt(seg-1);
          if (c == 0) {
              if (variableNext >= variableLimit) {
                  throw new RuntimeException("Variable range exhausted");
              }
              c = variableNext++;
              // Set a placeholder in the master variables vector that will be
              // filled in later by setSegmentObject().  We know that we will get
              // called first because setSegmentObject() will call us.
              variablesVector.add(null);
              segmentStandins.setCharAt(seg-1, c);
          }
          return c;
      }
docs: Return the standin for segment seg (1-based).