append_change = truefalse

True means append the index that changed to the Array. The default is false.

compile = truefalse

True means compile the iterator. The default is true.

rank = nonnegint

Specify the starting rank of the iterator. The default is one. Passing a value greater than one causes the iterator to skip the lower ranks; this can be useful when parallelizing iterators. The starting rank reverts to one when the iterator is reset, reused, or copied.

The SetPartitionGrayCode command returns an iterator that generates all partitions of a set of integers from one to n. The output consists of the restricted growth strings of length n in Gray code order.

A restricted growth string of length n corresponds to a partition of the set of integers 1 to n. Each integer in the output Array designates the set to which the index belongs; the sets are numbered starting at 0. For example, $⟨0\,0\,1\,2⟩$ corresponds to the partition $\left\{1\,2\right\},\left\{3\right\},\left\{4\right\}$.

$\mathrm{with}\left(\mathrm{Iterator}\right)\:$

$M≔\mathrm{SetPartitionGrayCode}\left(4\right)\:$

$\mathrm{Print}\left(M\,'\mathrm{showrank}'\right)\:$

 1: 0 0 0 0
 2: 0 0 0 1
 3: 0 0 1 1
 4: 0 0 1 2
 5: 0 0 1 0
 6: 0 1 1 0
 7: 0 1 1 2
 8: 0 1 1 1
 9: 0 1 2 1
10: 0 1 2 2
11: 0 1 2 3
12: 0 1 2 0
13: 0 1 0 0
14: 0 1 0 2
15: 0 1 0 1

$M≔\mathrm{SetPartitionGrayCode}\left(4\,'\mathrm{append\_change}'\right)\:$

$\mathrm{Print}\left(M\,'\mathrm{showrank}'\right)\:$

 1: 0 0 0 0
 2: 0 0 0 1
 3: 0 0 1 1
 4: 0 0 1 2
 5: 0 0 1 0
 6: 0 1 1 0
 7: 0 1 1 2
 8: 0 1 1 1
 9: 0 1 2 1
10: 0 1 2 2
11: 0 1 2 3
12: 0 1 2 0
13: 0 1 0 0
14: 0 1 0 2
15: 0 1 0 1

$\mathrm{Number}\left(M\right)$

$15$

Knuth, Donald Ervin. The Art of Computer Programming, volume 4, fascicle 3; generating all combinations and partitions, sec. 7.2.1.5, generating all set partitions, algorithm E, p. 127, ans. 14.

The Iterator[SetPartitionGrayCode] command was introduced in Maple 2016.

For more information on Maple 2016 changes, see Updates in Maple 2016.

The Iterator[SetPartitionGrayCode] command was updated in Maple 2022.

The n parameter was updated in Maple 2022.