array_recap.rb

# CRUD
musicians = [
  'Arjen Lucassen',
  'James LaBrie',
  'Steven Wilson',
  'Jeff Wayne'
]

# Create
musicians << 'John Lennon'

# Read
musicians[0] # => Arjen Lucassen

# Update
musicians[2] = 'Ringo'

# Destroy
musicians.delete('Ringo')
musicians.delete_at(2)

greet.rb

def greet(first_name, last_name)
  full_name = "#{first_name.capitalize} #{last_name.upcase}"
  yield(full_name)
end

greet_in_english = greet('john', 'lennon') do |name|
  "Hello, #{name}"
end
puts greet_in_english

greet_in_portuguese = greet('john', 'lennon') do |name|
  "E aí, #{name}?"
end
puts greet_in_portuguese

sing_gilberto_gil = greet('john', 'lennon') do |name|
  "Alô alô, #{name}. Aquele abraço!"
end
puts sing_gilberto_gil

range_recap.rb

musicians = [
  'Arjen Lucassen',
  'James LaBrie',
  'Steven Wilson',
  'Jeff Wayne'
]

# Print all musicians name's using for
# for
for name in musicians
  puts name
end

# Print all musicians name with for by using their index
# for
for i in 0...musicians.length
  puts musicians[i]
end

# Print list of the musicians with their position in the list
# #each_with_index
musicians.each_with_index do |musician, index|
  puts "#{index + 1}. #{musician}"
end

# Print all musicians names using #each
# #each
musicians.each do |musician|
  puts musician
end

# Create an array of musicians names upcased
# #map
musicians_upcased = musicians.map do |musician|
  musician.upcase
end
puts musicians_upcased

# Create an array with the first name of the musicians
# #map
musicians_first_name = musicians.map do |musician|
  musician.split.first
end

# Count the musicians that start with J
# #count
number_of_musicians_starting_with_j = musicians.count do |musician|
  musician.start_with?('J')
end
puts number_of_musicians_starting_with_j

# Extract the musicians that start with J
# #select
musicians_starting_with_j = musicians.select do |musician|
  musician.start_with?('J')
end
puts musicians_starting_with_j

# Extract the musicians that don't start with J
# #reject
musicians_not_starting_with_j = musicians.reject do |musician|
  musician.start_with?('J')
end
puts musicians_not_starting_with_j

timer.rb

def timer
  start_time = Time.now
  yield
  end_time = Time.now
  puts end_time - start_time
end

timer() do
  puts 'Counting even numbers'
  (0..10_000_000).count { |i| i.even? }
  puts 'Finished counting '
end

timer() do
  puts 'Waiting 1 second'
  sleep 1
  puts 'Finished waiting '
end