Picat List Comprehensions in Picat 3

Question 1

What is the Picat list comprehension that flattens [[1,2],[3,4],[5]] into [1,2,3,4,5]?

Accepted Answer

[X : L in [[1,2],[3,4],[5]], X in L]

Answer

flatten([[1,2],[3,4],[5]])

Answer

[X : X in [[1,2],[3,4],[5]]]

Answer

concat([[1,2],[3,4],[5]])

Question 2

How do you generate the 7-times multiplication table (7×1 through 7×10) as a list using a Picat list comprehension?

Accepted Answer

[7*X : X in 1..10]

Answer

mult_table(7, 10)

Answer

times(7, range(1,10))

Answer

[7 * X for X in range(1,11)]

Question 3

What does [X : X in [a,b,c,d,e], X \= b, X \= d] produce in Picat?

Accepted Answer

[a, c, e]

Answer

[b, d]

Answer

[a, b, c, d, e]

Answer

A syntax error because \= cannot appear in comprehension conditions

Question 4

Which expression correctly sums all elements in a list List using a list comprehension in Picat?

Accepted Answer

sum([X : X in List])

Answer

total([X : X in List])

Answer

add_all([X : X in List])

Answer

reduce(+, List, 0)

Question 5

Given a user-defined predicate is_prime/1, which Picat list comprehension generates all prime numbers up to 20?

Accepted Answer

[X : X in 2..20, is_prime(X)]

Answer

[primes(X) : X in 2..20]

Answer

primes_upto(20)

Answer

[X : is_prime(X), X in 2..20]

Question 6

What is the relationship between [X : X in L, true] and [X : X in L] in Picat?

Accepted Answer

They are equivalent because true always succeeds and filters out nothing

Answer

They are invalid; true is not a legal condition in Picat comprehensions

Answer

[X : X in L, true] returns only the first element of L

Answer

[X : X in L, true] converts every element to the atom true

Question 7

How many elements does [X : X in 1..5, Y in 1..5, X =:= Y] produce in Picat?

Accepted Answer

5 (one element for each pair where X equals Y)

Answer

25 (one element per combination in the Cartesian product)

Answer

0 (X and Y are distinct variables so =:= always fails)

Answer

10 (each matching pair is counted twice due to symmetry)