PLQ #9Done on: Tuesday, November 16th

Question 1 @ 2021-11-16 18:26

I’m worried about my PL grade, what should I do?

1
WORK HARDER!
2
Don’t worry about it, it’s an easy class.
3
My parents are paying for it, so whatever.
4
Go to Eli’s office hours and talk to him about it.
5
Don’t worry, be happy.
6
Don’t be happy, worry.

Question 2 @ 2021-11-16 18:31

In the compiled Toy language from last lecture, what would be the result of running the following program (assuming the usual global environment)?

{+ 1 n}

a

An unbound identifier error being thrown while the code is being compiled (a compile-time error).
b

An unbound identifier error being thrown after compilation, while the compiled form of the program is running (a run-time error).
c

An arithmetic error being thrown during run-time by the underlying Racket implementation.
d

1

Question 3 @ 2021-11-16 18:33

In some extended version of last week’s compiler, you see the following:

(define (compile expr)
...
(cases expr
...
[...
(if ...
(lambda ([env : ENV])
(error ...)) ; <---
(lambda ([env : ENV])
...))]
...))

What can you say about that error?

a
It’s a typical compile-time error.
b
It’s a typical run-time error.
c
It’s a typical type error.
d
It’s nonsensical code.
e
It’s a case where we know that there’s an error at compile-time, but need to defer throwing it at run-time for whatever reasons.

Question 4 @ 2021-11-16 18:36

What will the following produce?

#lang pl lazy

(define foo
(append (list 1 2)
(map (lambda (x) (append x x))
foo)))
(take 2 foo)

a
It will get stuck in an infinite loop.
b
It will throw a type error.
c
It will return (1 2).
d
It will return (1 1).
e
It will fail typechecking.

Question 5 @ 2021-11-16 18:38

What will the following produce?

#lang pl lazy

(define foo
(append (list 1 2)
(map (lambda (x) (append x x))
foo)))
(take 4 foo)

a
It will get stuck in an infinite loop.
b
It will throw a (runtime) type error.
c
It will return (1 2 1 2).
d
It will return (1 1 2 2).
e
It will fail typechecking.