Picat The Planner Module 3

Question 1

What type constraint applies to the Cost argument in `action(State, NextState, Action, Cost)`?

Accepted Answer

It must be a non-negative number

Answer

Cost must be a non-negative numeric value; negative costs are not supported and would prevent the planner from terminating.

Question 2

What happens when `plan/2` cannot find any plan from the given initial state?

Accepted Answer

The call fails

Answer

Like most Picat predicates, `plan/2` simply fails (backtracks) when no plan exists rather than throwing an error.

Question 3

Which predicate finds a cost-optimal plan in Picat's planner module?

Accepted Answer

best_plan/2

Answer

`best_plan(State, Plan)` searches for the plan with the minimum total cost among all valid plans.

Question 4

How should states be represented in Picat planning problems for best performance?

Accepted Answer

As ground (fully instantiated) terms

Answer

Ground terms allow the planner to efficiently hash and detect previously visited states, preventing redundant exploration.

Question 5

What does `plan_unbounded/2` do differently from `plan/2`?

Accepted Answer

It searches without any cost bound, potentially exploring all reachable states

Answer

`plan_unbounded/2` imposes no upper cost limit on the search, whereas `plan/2` uses iterative deepening with increasing cost bounds.

Picat Practice Test