my $p = UnorderedSetPartition->new(
           items => ['a'..'f'],
           blocks => [2,2,1,1],  ## arrayref list of blocks, num of blocks, or omitted=unrestricted
        );

my $p = OrderedSetPartition->new(
           items => ['a'..'f'],
           blocks => [2,2,1,1],  ## arrayref list of blocks, num of blocks, or omitted=unrestricted
        );


## or perhaps:
## SetPartition->new( ... ordered => 0 ... );

my $iter = $p->iterator(
               order => "lex",  ## "lex", "colex", "gray", "fastest", etc...
               representation => "rg",  ## "rg", "AoA", etc..
           );

@output = $iter->next;
$iter->skip($n);
$iter->prev; # ??

$iter->reset; ## to the beginning
$iter->reset( $some_saved_rank_or_widget );

####

@output = $p->list( order => "lex", representation => "rg" );
## same as iterator, but returns list of *all* widgets
## maybe allow for a callback

####

$r = $p->rank( order => "lex", representation => "rg", $widget );
$widget = $p->rank( order => "lex", representation => "rg", $r );
## code repetition here?

$how_many_partitions = $p->count;