ruby-quiz.md

Ruby Quiz

Q1 - What’s a variable? What’s the point of using variables? Give an example.

Name for a value in memory. Retrieving values for later use.

age = 18
age # => 18

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Q2 - Precisely describe the following line of code *using the correct vocabulary*.

Assigning 18 to age (saying "storing" is fine, but less precise).

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Q3 - What’s a method? What’s the point of defining methods?

It's a piece of code with a name, which can receive values to use as parameters for their execution. We define them for re-usability and naming chinks of code can help with code clarity.

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Q4 - Precisely describe what happens at *each line* using good vocabulary. Write a ruby comment next to the line you’re explaining using the #.

def multiply(x, y) # define multiply, with the parameters x and y
  return x * y     # return the product of x and y's values
end                # close the method block

puts multiply(5, 8) # calling the method multiply with arguments 5 and 8, and printing its return value with puts

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Q5 - What’s the keyword if ? Give us an example of if statements, using an age variable storing a student’s age for instance.

# if starts a conditional statement (controls the flow of the code)
age = 18
puts "You can vote if" if age > 18

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Q6 - Complete the following code to compute the *exact* average of students grades (using each ).

grades = [19, 8, 11, 15, 13]
sum = 0
grades.each do |grade|
  # grade => 19
  sum += grade
end
sum.to_f / grades.size # sum

# ====== OR ======
grades.sum.to_f / grades.size #sum

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Q7 - Define a capitalize_name method which takes first_name and last_name as parameters and returns the well-formatted fullname (with capitalized first and last names).

def capitalize_name(first_name, last_name)
  "#{first_name.capitalize} #{second_name.capitalize}"
end

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Q8 - What’s the difference between *concatenation* and *interpolation*? Give an example.

Concatenation joins two different string (usually with just a +) together. Interpolation allows us to run code inside a string.

"Name" + "Other name" # concatenation
"2 + 2 = #{2 + 2}"    # interpolation

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Q9 - Translate each line of pseudo-code into ruby.

fruits = ["banana", "peach", "watermelon", "orange"]

# Print out "peach" from the fruits array in the terminal
print fruits[1]

# Add an "apple" to the fruits array
fruits << "apple"

# Replace "watermelon" by "pear"
fruits[2] = "pear"

# Delete "orange"
fruits.delete_at(3)
fruits.delete_at(-2)

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Q10 - Translate each line of pseudo-code into ruby.

city = { name: "Paris", population: 2000000 }

# Print out the name of the city
print city[:name]

# Add the Eiffel Tower to city with the `:monument` key
city[:monument] = "Eiffel Tower"

# Update the population to 2000001
city[:population] = 2_000_001
# city[:population] += 1

# What will the following code return?
city[:mayor] # => nil

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Q11 - Use the map iterator to convert the variable students, an array of arrays, into an array of hashes. Those hashes should have two keys: :name and :age. What is the type of those keys?

students = [ [ "john", 28 ], [ "mary", 25 ], [ "paul", 21 ] ]

students.map do |student_arr|
  #                     0     1
  # student_arr => [ "john", 28 ]
  name = student_arr[0]
  age  = student_arr[1]
  { name: name, age: age }
end