Picat Logic Programming and Unification 2

Question 1

In Picat, what happens when unification of two terms fails during pattern matching in a clause head?

Accepted Answer

Picat backtracks and tries the next matching clause

Answer

When a clause head fails to unify with the call, Picat backtracks and attempts the next clause whose head can unify.

Question 2

Which Picat operator is used to check structural equality without performing unification?

Accepted Answer

==

Answer

The == operator tests if two terms are identical in structure and variable bindings without unifying them.

Question 3

In Picat logic predicates, what does the goal `X = f(Y), Y = 3` result in for X?

Accepted Answer

X = f(3)

Answer

After Y unifies with 3, the earlier binding X = f(Y) propagates so X becomes f(3).

Question 4

What is the role of the anonymous variable `_` in Picat unification?

Accepted Answer

It matches any term and is never shared across occurrences

Answer

Each occurrence of _ is a distinct fresh variable that matches anything but shares no binding with other _ occurrences.

Question 5

Which of the following Picat goals will succeed?

Accepted Answer

f(X,Y) = f(1,2)

Answer

f(X,Y) = f(1,2) succeeds by binding X=1 and Y=2; the other options fail due to structural or value mismatches.

Picat Practice Test