massive changes to add a 'zipper' representation of C-- Wed Aug 15 11:07:13 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Mon Aug 20 19:22:14 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Mon Aug 20 20:54:41 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Tue Aug 21 18:09:13 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Wed Aug 22 16:41:58 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Thu Aug 23 13:44:49 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Thu Aug 23 14:07:28 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Fri Aug 24 17:27:04 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Fri Aug 24 19:35:03 BST 2007 Norman Ramsey <nr@eecs.harvard.edu> Fri Aug 31 14:38:02 BST 2007 Norman Ramsey <nr@eecs.harvard.edu>