// only shift-right supported so far
srecord noeq OnePathShifter(OnePathWithOrigin path, bool shiftRight) { 
  Pt p;
  Pt direction;
  int iStep;
  gettable OnePathWithOrigin outPath;
  
  run {
    assertTrue(shiftRight);
    outPath = new OnePathWithOrigin;
    p = path.origin();
    
    while (iStep < path.nSteps()) {
      // TODO
      ++iStep;
    }
  }
  
  OnePathWithOrigin get() { if (outPath == null) run(); ret outPath; }
}