anchor.diff:           singleton/1,
            skip/2,
            skipWhile/2,
  -         %sort/1,
  +         sort/1,
            %sortBy/2,
            sum/1,
            %sumBy/2,
  
positive.code:     [1,2,3] = toList(Low),
      ok.
  
  distinct_test() ->
      Seq = [1,2,3,3,2,1],
      [1,2,3] = toList(distinct(Seq)),
      [1,2,3] = toList(distinctBy(fun id/1, Seq)),
      [1,2,3] = toList(distinctBy(fun(N) -> N*N end, Seq)),
  
      ok.
  
  windowed_test() ->
  
negative.code:     Seq = [1,2,3],
      3 = countBy(fun id/1, Seq),
      1 = countBy(fun(_) -> one end, Seq),
      ok.
  
  sort_test() ->
      Seq = [2,1,3],
      [1,2,3] = toList(sort(Seq)),
      ok.
  
  are_seqs_test() ->
  