12.10 Some of the operations in standard programming languages can be modelled as actions that change the state of the world. For example, the assignment operation changes the contents of a memory location; the print operation changes the state of the output stream. A program consisting of these operations can also be considered as a plan, whose goal is given by the specification of the program. Therefore, planning algorithms can be used to construct programs that achieve a given specification.

a. Write an operator schema for the assignment operator (assigning the value of one variable to another).

b. Show how object creation can be used by a planner to produce a plan for exchanging the values of two variables using a temporary variable.