Question 1

In Ruby, which of the following literals correctly creates a Hash object with default values for undefined keys?

Options :

A : hash = { default: [] }

B : hash = Hash.new { |h, k| h[k] = [] }

C : hash = Hash[:default, 0]

D : hash = {}.default(0)

Answer: B

Question 2

In Ruby programming, the correct use and understanding of operators is essential. Analyze the following Ruby code snippet:

a = 8b = 4result1 = a != bresult2 = a & b == 4result3 = (a * 2) / b Based on this code, which two of the following statements are true regarding the use and precedence of the operators?

Options :

A : result2 is true as the bitwise AND (&) operation has higher precedence than the equality (==) operator.

B : result1 evaluates to true because != checks if a and b are not equal.

C : result1 is false since != is a strict inequality operator and a is greater than b.

D : In result2, the equality (==) operation is evaluated before the bitwise AND (&) operation.

E : result3 equals 4 because division (/) has higher precedence than multiplication (*).

Answer: B,D

Question 3

Analyze the following Ruby code snippet in the context of class design and instance variable management:

class Book

attr_reader :title, :author

@@total_books = 0

def self.total_books

@@total_books

end

def initialize(title, author)

@title = title

@author = author

@@total_books += 1

end

class Library

attr_reader :books

def initialize

@books = []

end

def add_book(book)

@books << book

end

def total_books_in_library

@books.size

end

library = Library.new

library.add_book(Book.new("1984", "George Orwell"))

library.add_book(Book.new("To Kill a Mockingbird", "Harper Lee"))

result1 = Library.total_books

result2 = library.total_books_in_library

What will be the values of result1 and result2, respectively?

Options :

A : undefined method 'total_books' for Library:Class, undefined method 'total_books_in_library' for Library:Class

B : 2, undefined method 'total_books_in_library' for Library:Class

C : undefined method 'total_books' for Library:Class, 2

D : 2, 2

Answer: C

Question 4

In Ruby, effectively using blocks is essential for controlling flow and data processing. Review the following Ruby code snippet:

numbers = [1, 2, 3, 4, 5]sum = 0numbers.each { |number| sum += number }squared_numbers = numbers.map { |number| number ** 2 } Based on this code, which two of the following statements are correct about the blocks used in the context of the each and map methods?

Options :

A : The each block creates a new array containing each number squared.

B : The map block returns a new array with the square of each number, while the original numbers array remains unchanged.

C : Both each and map blocks modify the original numbers array.

D : The each block iteratively adds each number in the numbers array to sum, resulting in the sum of all numbers.

E : The map block modifies the original numbers array to contain the square of each number.

Answer: B,D

Question 5

In Ruby, the use of blocks is a fundamental concept for iterating over collections and executing code repeatedly. Examine the following Ruby code snippet:

numbers = [1, 2, 3, 4, 5]sum = 0numbers.each { |number| sum += number }doubled = numbers.map { |number| number * 2 } Based on this code, which two of the following statements are true regarding the use and functionality of blocks?

Options :

A : The each block creates a new array with each number in numbers incremented by 1.

B : Both each and map blocks modify the original numbers array.

C : The each block increments sum by each number in the numbers array, resulting in the sum of all elements.

D : The map block modifies the original numbers array to contain each number doubled.

E : The map block returns a new array with each number in numbers doubled, leaving the original array unchanged.

Answer: C,E

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