In addition, hand in hard copies of your source code and sample runs. Name your programs with the .lsp suffix.
L returns the number of s-expressions in the list.
Write a function, exists , which when given a list of atoms L, an atom x , and an integer n , returns true if the nth element of the list is equal to x. Rewrite the function using the DO structure this time. The function should take as arguments the graph, the starting node and the goal node and return as output the path from the start to the goal.