PLQ #4Done on:   Tuesday, February 15th

Question 1 @ 2022-02-15 18:58

Consider this FLANG code:

What must be true of THING?

(Choose the best answer.)

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• 1
  THING must be a function form.
• 2
  THING must evaluate to a function value.
• 3
  THING must fit on one line.
• 4
  THING must evaluate to a number.
• 5
  THING must be valid FLANG expression.
• 6
  THING can be anything.

Question 2 @ 2022-02-15 19:01

We briefly discussed de Brujin Indexing in lecture. In the program below, how would we convert this to a program that uses de Brujin Indices?

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• 1
  {with 4 {with 7 {with 2 {- [0] [1] [2]}}}}
• 2
  {with 2 {with 7 {with 4 {- [0] [1] [2]}}}}
• 3
  {with 4 {with 7 {with 2 {- [2] [1] [0]}}}}
• 4
  {with 2 {with 7 {with 4 {- [2] [1] [0]}}}}
• 5
  None of the above

Question 3 @ 2022-02-15 19:02

Which of the following is true about “first-class” functions?

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• 1

  Our FLANG language has higher-order functions rather than first-class functions.

• 2

  First-class functions can be created at runtime.

• 3

  First-class functions can be produced in C if the program uses function pointers in the arguments.

• 4

  First-class functions must be bound to an identifier (be named) so we can use them.

• 5

  First-order functions are synonymous with First-class functions.

Question 4 @ 2022-02-15 19:05

Last week, we added functions to our language. The first shot we had at implementing the evaluation rules had:

Which of the following tests will throw an error for this implementation?

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• 1
  {call {fun {x} {+ x 3}} 7}
• 2
  {with {add3 {fun {x} {+ x 3}}}
    {call add3 7}}
• 3
  {with {add1 {fun {x} {+ x 1}}}
    {with {add3 {fun {x} {+ x 3}}}
      {call add3 {call add1 7}}}}
• 4
  {with {id {fun {x} x}}
    {with {add3 {fun {x} {+ x 1}}}
      {call {call id add3} 5}}}
• 5
  {with {sqr {fun {x} {* x x}}}
    {+ {call sqr 5}
      {call sqr 6}}}

Question 5 @ 2022-02-15 19:09

From the class notes, showing off some of the things that you can do with first-class functions:

How would you correctly call the above currify function to add two numbers?

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• 1
  (currify add 1 2)
• 2
  (currify (add 1 2))
• 3
  ((currify add) 1 2)
• 4
  (((currify add) 1) 2)
• 5
  ((currify add) (1 2))
• 6
  ((currify add) (list 1 2))