I need a function to filter the Permutations.

 

For example:

 

(gen-divide 2 (flatten (permute (pcs '4-1))))

 

Will result in:

 

((0 1) (2 3) (0 1) (3 2) (0 2) (1 3) (0 2) (3 1) (0 3) (1 2) (0 3) (2 1) (1 0)
 (2 3) (1 0) (3 2) (1 2) (0 3) (1 2) (3 0) (1 3) (0 2) (1 3) (2 0) (2 0) (1 3)
 (2 0) (3 1) (2 1) (0 3) (2 1) (3 0) (2 3) (0 1) (2 3) (1 0) (3 0) (1 2) (3 0)
 (2 1) (3 1) (0 2) (3 1) (2 0) (3 2) (0 1) (3 2) (1 0))

 

But I don't mind with the order, since I'll make chords out of it, so

 

((0 1) (2 3) or (0 1) (3 2) or (1 0) (2 3)  will result in the same chord.

 

How to filter the list onto a list where the order does not matter ?

 

Best,

 

Julio

 

Possible workaround:

 

(remove-duplicates (sort-asc (combination 3 (pcs '6-1))) :test #'equal)

 

as well:

 

(find-unique (sort-asc (combination 3 (pcs '6-1))))

Thanks, Janusz !