Looping Behaviour

First, observe that to simulate depth first search we simply modify the definition of agenda_putl/3 (this puts a list of expanded items onto the agenda) from

agenda_putl(A,L,Anew) :- append(A,L,Anew).

to

agenda_putl(A,L,Anew) :- append(L,A,Anew).

The algorithm loops

• When DFS is used.
• It also loops with BFS if asked to find a path that does not exist.

Checkpoint. Verify both of these assertions.