// Both lines and columns are numbered from 1
sclass LineAndColumn {
  int line, col;
  
  *(int *line, int *col) {}
  
  // get text of a line. may return null if no text available
  swappable S getLineText(int line) { null; }
  
  toString { ret "Line " + n2(line) + ", col " + n2(col); }
}