Clojure Functions (L17)

Question 1

Where is the optional “doc string” placed when documenting a Clojure function?

Answer 1

Between the function name and the parameter sequence.

Question 2

How are doc strings typically formatted?

Answer 2

As a multi line string, the first line being a summary and the remaining lines providing details.

Question 3

What Clojure form displays the documentation of a specified function?

Answer 3

(doc myFunc)

Question 4

What are Codox, Marginalia, and Cadastre?

Answer 4

These are third party tools that prepare indexed, web-based documentation from documented Clojure source code.

Question 5

What is a function’s arity?

Answer 5

It is the number of parameters that function accepts.

Question 6

Arity overloading occurs by defining separate versions of the same function that take a different of arguments.

Answer 6

False, arity overloading occurs within the same function definition.

Question 7

Different arities of the same function can call one another.

Answer 7

True.

Question 8

The following is a valid example of arity overloading.
(defn fname
[arg1] (expression1)
[arg1 arg2] (expression2))

Answer 8

False:
(defn fname
([arg1] (expression1))
([arg1 arg2] (expression2)))

Question 9

Functions in Clojure may be passed as parameters without any special syntax.

Answer 9

True.

Question 10

What does Clojure’s map function do?

Answer 10

It applies a specified function argument to each element of an associated sequence.

Question 11

What does Clojure’s reduce function do?

Answer 11

Applies a specified function parameter to all elements of a sequence in order to produce a single value.

Question 12

What does the following return?
(reduce + [1 2 3])

Answer 12

6

Question 13

What does the following return?
(reduce + 1 [1 2 3])

Answer 13

7

Question 14

What does Clojure’s filter function do?

Answer 14

Applies a specified function parameter to all elements of a sequence in order to extract elements that match the filter.

Question 15

Must the function passed to Clojure’s filter return a Boolean?

Answer 15

No.

Question 16

How can a function return another function?

Answer 16

By placing the definition of the function to return at the end of the outer function definition.

Question 17

What is a closure in Clojure?

Answer 17

These are partially instantiated functions that store variables in the scope of the outer function.

Question 18

What do Clojure’s “first” and “rest” functions do?

Answer 18

These return the first element of a specified sequence, or all but the first element of a specified sequence, respectively.

Question 19

Clojure’s “cons” function constructs a new list/vector by prepending the item to the existing sequence.

Answer 19

False, it always constructs a new list by prepending the item to the existing sequence.

Question 20

What does Clojure’s “take” and “drop” functions do?

Answer 20

These return a list of the first n elements of the sequence, and return a list with the first n elements of the sequenced removed, respectively.

Question 21

“cons”, “take”, and “drop” always return a list, rather than a vector.

Answer 21

True.

Question 22

Which Clojure function extracts the elements from a sequence until the specified function is no longer true (truthy)?

Answer 22

take-while

Question 23

Which Clojure function removes the elements from a sequence until the specified function is no longer true (truthy)?

Answer 23

drop-while

Question 24

What is returned by the following?
(take-while #(< % 5) [3 6 1 4 7])

Answer 24

(3)

Question 25

What is returned by the following?
(drop-while #(< % 5) [3 6 1 4 7])

Answer 25

(6 1 4 7)

Question 26

(some func sequence) returns true or false depending on whether func specifies at least one element in the sequence.

Answer 26

False, it returns the first truthy value or nil
otherwise.

Question 27

(concat s1 s2) always returns a list containing s1 and s2’s elements, regardless of the sequence types of s1 and s2.

Answer 27

True.

Question 28

The following is valid and returns a sorted vector:
(sort [4 5 2 7])

Answer 28

False, sort always returns a list.

Question 29

The following is valid and returns a sorted list:
(sort [“d” “ab” “a”])

Answer 29

True.

Question 30

The following is valid and returns a sorted list:
(sort [“d” “ab” 1 “a”])

Answer 30

False, you can’t mix types.

Question 31

Does the following return a list sorted in increasing or decreasing order?
(sort #(> %1 %2) [3 1 4 6 7])

Answer 31

Decreasing.

Question 32

Does the following return a list sorted in increasing or decreasing order?
(sort #(< %1 %2) [3 1 4 6 7])

Answer 32

Increasing.

Question 33

Does the following return a list sorted in increasing or decreasing order?
(sort #(< %2 %1) [3 1 4 6 7])

Answer 33

Decreasing.

Question 34

Does the following return a list sorted in increasing or decreasing order?
(sort #(> %2 %1) [3 1 4 6 7])

Answer 34

Increasing.

Question 35

What does the following return?
(into [ ] ‘(1 2 3 4))

Answer 35

[1 2 3 4]

Question 36

What does the following return?
(into ‘( ) [1 2 3 4])

Answer 36

(4 3 2 1)

Question 37

What does the following return?
(into ( ) [1 2 3 4])

Answer 37

(4 3 2 1)

Question 38

Are the following lines valid?
(into ‘( ) ‘(1 2 3))
(into ( ) ‘(1 2 3))

Answer 38

Yes - both return (3 2 1).

Question 39

Is the following line valid?
(into [ ] [1 2 3])

Answer 39

Yes.

Question 40

The following lines take the same speed to execute:
(first (range 1000000))
(last (range 1000000))

Answer 40

False - Clojure employs lazy sequences, meaning the first line is nearly instant (much faster).