00100	Proposed extensions
00200	
00300	1. Suppose there are too many successors to make a list.  Then
00400	a successor generator can be used that gives a new successor
00500	only when it needs to be tried.
00600	
00700	2. An update-revert scheme can be hidden under a
00800	successor function or successor generator.
00900	
01000	3. To get sequence solitaire, the search scheme has to be
01100	able to deal with uncertainty.
01200	
01300	4. Get Carnegie chess program.
01400	
01500	5. Incorporate killer heuristic.