Picat Data Structures and Types 4

Question 1

Which operator decomposes a compound term into a list `[Functor | Args]` in Picat?

Accepted Answer

=.. (the univ operator)

Answer

The `=..` (univ) operator decomposes `f(a,b)` into `[f, a, b]` and can also construct terms from such lists.

Question 2

What does `f(a, b, c) =.. L` bind L to in Picat?

Accepted Answer

[f, a, b, c]

Answer

The univ operator produces a list whose head is the functor and whose tail is the argument list: `[f, a, b, c]`.

Question 3

What does `arg(1, point(3, 4), X)` bind X to in Picat?

Accepted Answer

3

Answer

`arg/3` is 1-indexed in Picat: arg 1 of `point(3,4)` is `3`, the first argument.

Question 4

Which predicate extracts the functor name and arity from a compound term?

Accepted Answer

functor(T, F, A)

Answer

`functor(T, F, A)` binds F to the principal functor of T and A to its arity.

Question 5

What does `compound(hello)` evaluate to in Picat?

Accepted Answer

false

Answer

`compound/1` fails for atoms like `hello` — a compound term must have a functor and at least one argument.

Picat Practice Test