t...@sevak.isi.edu (Thomas A. Russ) writes: > "Pascal J. Bourguignon" <p...@informatimago.com> writes: > >> t...@sevak.isi.edu (Thomas A. Russ) writes: >> > >> > This will only work if there is a backpointer to the parent. >> >> No, you don't need backpointers; some cases have been mentionned in the >> other answer, but in general: >> >> (defun parent (tree node) >> (if (member node (children tree)) >> tree >> (some (lambda (child) (parent child node)) (children tree)))) >> >> Yes, the question wasn't about time complexity. > > :-p > > Um, this is a recursive function. Inside PARENT, there is another call > to PARENT.
Feel free to derecursive it. -- __Pascal Bourguignon__ http://www.informatimago.com/ A bad day in () is better than a good day in {}. -- http://mail.python.org/mailman/listinfo/python-list
