> The "pair" is a (value+pointer), and sometimes "value" can itself be a pointer. So when you have (pointer, pointer), you now can create trees. Pointers don't

> The "pair" is a (value+pointer), and sometimes "value" can itself be a pointer. So when you have (pointer, pointer), you now can create trees. Pointers don't always imply trees. Any Lisp object that won't directly fit in half a cons cell gets allocated separately and a pointer to it is placed in that half of the cons cell. Examples: Strings, symbols, bignums, etc. > If you need "more" than this (ie: graphs), then perhaps its insufficient. You can certainly represent cyclic graphs with cons cells. The *print-circle* mechanism in Common Lisp handles printing them, for example.