PLQ #4

Question 1 @ 2025-02-04 18:18

What does it mean for functions to be a first-class citizens in a programming language?

A Functions can only be used as values
B Functions can only be used as arguments to other functions
C Functions are created at compile-time
D Functions are values that can be passed to & returned from functions, and created at run-time
E Functions can only be defined and called by their name

Question 2 @ 2025-02-04 18:23

Which of the following are true about different treatments of functions in programming languages?

FOV
First order: functions can be used as values
FOS
First order: function values can be created in any scope
HOV
Higher order: functions can be used as values
HOS
Higher order: function values can be created in any scope
FCV
First class: functions can be used as values
FCS
First class: function values can be created in any scope

Question 3 @ 2025-02-04 18:26

What would be the result of running this expression using our Flang language implementation (the one with substitutions)?

{with {+ *} {+ 1 2}}

A Compilation error
B 2
C 3
D Unbound + error
E Unbound * error
F bad with syntax in

Question 4 @ 2025-02-04 18:30

Given the following code and one sample test:

(define (fix1 f x)
(lambda (y) (f x y)))

(test ((fix1 mul 10) 5) => 50)

Which of the following type declarations is best for fix1?

A (: fix1 : (All (A B) (A A -> B) -> A -> B))
B (: fix1 : (All (A B) (A A -> B) A -> (A -> B)))
C (: fix1 : (All (A B C) (A B -> C) A -> (B -> C)))
D (: fix1 : (All (A B C) (A B -> C) -> (A -> (B -> C))))
E (: fix1 : (All (A B C) (A B -> C) -> A -> (B -> C)))
F (: fix1 : (All (A B C) (A B -> C) (A -> B) -> C))

Question 5 @ 2025-02-04 18:34

Which of the following FLANG expressions are equivalent in terms of how they get evaluated (ie, ignoring substitutions on the way)?

(A) {+ E1 E2}
(B) {with {x E1} {with {y E2} {+ x y}}}
(C) {with {y E2} {with {x E1} {+ x y}}}

(Be careful when you think about it.)

None None are equivalent
AB A is equivalent to B
AC A is equivalent to C
BC B is equivalent to C
ABC All three are equivalent
Trick Trick question: the answer depends on Racket’s behavior