3 ms·

What's wrong with (A (B C) C D) ? For circular structures, you could also have: '#1=(A . #1#) Which is: (A A A A A A A ....)

• chriswarbo 10y ago
  > What's wrong with (A (B C) C D) ? That's a different structure: it has two Cs in it. > For circular structures, you could also have: '#1=(A . #1#) That's what I meant by "references".
  • junke 10y ago
    > That's a different structure: it has two Cs in it. It has two occurrences of the same C (but maybe I did not get your example).