• Data Structures. The state representation of the 8-puzzle 1s close to the representation
one could find in a specialized pro gram. However, the same cannot be said for Towers
of Hanoi. In a specialized program, the state would not be represented by a set of equalities
loc(diski) = diskj, but by three lists (disk1 , disk2, .. .) one for each peg, meaning that
disk1 is on disk2 which is on disk3 , etc. Then the action of moving a disk from one peg
to another would be implemented as operations on the heads of t hese lists. One way to
achieve such efficient representations in FStrips is by al lowing Lists as primitive types. Then
functions like car, cdr , cons , etc. defined in the underlying language can be made available
in the planning language. This would allow high-level representa tions of Tower of Hanoi and
other problems that are as efficient as sp ecialized representations.