anchor.diff:  /** Pads [source] to [length] by adding spaces at the end. */
   String padRight(String source, int length) {
     final result = new StringBuffer();
  -  result.add(source);
  +  result.write(source);
   
     while (result.length < length) {
  -    result.add(' ');
  +    result.write(' ');
     }
   
     return result.toString();
  -}+}
  
positive.code:   writeLine(int column, String text) {
      // Write any pending newlines.
      while (newlinesNeeded > 0) {
        buffer.add('\n');
        newlinesNeeded--;
      }
  
  
negative.code:     // to the next line.
      while (currentColumn != column) {
        if (currentColumn < NUM_COLUMNS - 1) {
          buffer.write(padRight('', columnWidths[currentColumn]));
        } else {
          buffer.write('\n');
        }
        currentColumn = (currentColumn + 1) % NUM_COLUMNS;
      }
  
      if (column < columnWidths.length) {
        // Fixed-size column, so pad it.
        buffer.write(padRight(text, columnWidths[column]));
      } else {
        // The last column, so just write it.
        buffer.write(text);
      }
  
      // Advance to the next column.
  