Functions vs. Predicates Flashcards

Which syntax correctly defines a Picat function that returns the square of X?

Answer: square(X) = X * X

Picat functions are defined with `=` between the head and the return expression.

In Picat, what happens when you call a function but no clause pattern matches the arguments?

Answer: An existence error or pattern-match failure is thrown

If no function clause matches, Picat raises an exception because functions must return a value.

A Picat predicate clause uses `?=>` instead of `=>`. What does this indicate?

Answer: The predicate is nondeterministic and may leave choice points

`?=>` marks a nondeterministic clause that keeps a choice point, allowing backtracking.

Can a Picat function be embedded directly inside an arithmetic expression such as `Y = f(X) + 3`?

Answer: Yes, because functions return values usable in expressions

Picat functions return values and can appear anywhere an expression is expected.

Which of the following is a valid way to call a Picat predicate `greet(Name)`?

Answer: greet("Alice")

Predicates are called as statements; they do not return values and cannot appear inside expressions.

In Picat, the body of a function clause and the body of a predicate clause share which feature?

Answer: Both can include goals, assignments, and conditionals

Both function and predicate bodies are sequences of goals and can use the same control constructs.

What is the correct way to define a recursive Picat function `fact(N)` for the factorial of N?

Answer: fact(0) = 1. fact(N) = N * fact(N-1).

Recursive Picat functions use `=` and pattern-match across multiple clauses.