Tail-Recursive Search

The search algorithm can also be written in a tail-recursive style.

• The path (sequence of operators) to the goal is passed down as a variable, initially '().

• Each time an operator op is applied to create a new state, op is consed onto the path for the recursive call. Since cons acts as a stack and makes a list in backwards order, the path is a backwards list of operators taken from the start.

• When the goal is found, a reverse of the path gives a solution (sequence of operators to get from the start to the goal).