Data Structures and Types Flashcards

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

Answer: =.. (the univ operator)

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

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

Answer: [f, a, b, c]

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

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

Answer: 3

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

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

Answer: functor(T, F, A)

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

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

Answer: false

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

What does `copy_term(f(X, X), Copy)` produce in Picat?

Answer: Copy = f(_A, _A) with a single new shared variable

`copy_term/2` creates a renamed copy: both positions of X become the same new variable _A, preserving sharing.

What is the arity of the Picat term `foo(a)`?

Answer: 1

Arity is the number of arguments a compound term takes; `foo(a)` has exactly one argument, so its arity is 1.