Comments on Search Algorithm
- The program continually goes deeper until it reaches a terminal
state, which is either a goal or a failure.
- When the goal is found, search returns '()
as its answer. This is an empty list of operators, since no
operators are required to reach the goal.
- At each level as the search unwinds, the operator used
at that level is put onto the front of the operator list using
cons. cons adds a new item onto the front of a list:
(cons 'a '(b c)) = (A B C)