anchor.diff:          }
       }
       $dart$core.int _$from;
  -    List sublistFrom([$dart$core.int from]) => (() {
  -        if (from > 0) {
  -            return new List$Rest($outer$ceylon$language$List, from + this._$from);
  -        } else {
  -            return this;
  -        }
  -    })();
  -    $dart$core.Object getFromFirst([$dart$core.int index]) => (() {
  -        if (index < 0) {
  -            return null;
  -        } else {
  -            return $outer$ceylon$language$List.getFromFirst(index + _$from);
  -        }
  -    })();
  +    List sublistFrom([$dart$core.int from]) => from > 0 ? new List$Rest($outer$ceylon$language$List, from + this._$from) : this;
  +    $dart$core.Object getFromFirst([$dart$core.int index]) => index < 0 ? null : $outer$ceylon$language$List.getFromFirst(index + _$from);
       $dart$core.int get lastIndex => (() {
           $dart$core.int size = $outer$ceylon$language$List.size - _$from;
           return size > 0 ? size - 1 : null;
  
positive.code:     $dart$core.String toString();
      static $dart$core.String $get$string([final Iterable $this]) => (() {
          Sequential elements = $this.take(31).sequence();
          return (() {
              if (elements.empty) {
                  return "{}";
              } else {
                  return (() {
                      if (elements.size == 31) {
                          return ("{ " + $package$commaList(elements.take(30))) + ", ... }";
                      } else {
                          return ("{ " + $package$commaList(elements)) + " }";
                      }
                  })();
              }
          })();
      })();
  }
  $dart$core.String $package$commaList([Iterable elements]) => (() {
  
negative.code:     Sequential get rest => _$firstSeq.rest.append(_$secondSeq);
      $dart$core.Object getFromFirst([$dart$core.int index]) => (() {
          $dart$core.int cutover = _$firstSeq.size;
          return index < cutover ? _$firstSeq.getFromFirst(index) : _$secondSeq.getFromFirst(index - cutover);
      })();
      Tuple slice([$dart$core.int index]) => index == _$firstSeq.size ? new Tuple.$withList([_$firstSeq, _$secondSeq]) : Sequence.$slice(this, index);
      Sequential spanTo([Integer to]) => Integer.nativeValue(to) == (_$firstSeq.size - 1) ? _$firstSeq : Sequence.$spanTo(this, to);
      Sequential spanFrom([Integer from]) => Integer.nativeValue(from) == _$firstSeq.size ? _$secondSeq : Sequence.$spanFrom(this, from);
      Sequential measure([Integer from, $dart$core.int length]) {
          if ((Integer.nativeValue(from) == 0) && (length == _$firstSeq.size)) {
              return _$firstSeq;
  