array.rb

def call_block
  puts "Start of method"
  yield
  yield
  yield
  puts "End of method"
end

say_goodnight.rb

$greeting = "Hello"
@name = "Prudence"
def say_goodnight name
  "Good night #{name.capitalize}"
end

a = [1, 'cat', 3.14]
b = %w{ant bee cat dog elk}
print b, "\n"
a[2] = nil
print a, "\n"

puts say_goodnight 'lifulei'

puts "#$greeting, #@name"

#while line = gets
# puts line.downcase
#end


line = "Perl"
#if line =~ /Perl|Python/
#  puts "Scripting language mentioned: #{line}"
#end

newline = line.sub(/Perl/, 'Ruby')

puts newline

animals = %w{ ant bee cat dog elk }
def call_block
  puts "Start of method"
  yield
  puts "End of method"
end
call_block {|str| puts animals }

animals.each {|name| print name, " " }

5.times { print "*"}

3.upto(6) {|i| print i}

('a'..'e').each {|char| print char}
puts " "
printf("Number: %5.2f, \nString: %s\n", 1.23, "hello")

line = gets
print line
print

song.rb

class Song
  @@plays = 0
  def initialize(name, artist, duration)
    @name = name
    @artist = artist
    @duration = duration
    @plays = 0
  end

  attr_reader :name, :artist, :duration
=begin

  def name
    @name
  end

  def artist
    @artist
  end

=end

  attr_writer :name, :duration
=begin
  def duration=(new_duration)
    @duration = new_duration
  end
=end

  def duration_in_minutes
    @duration/60
  end

  def duration_in_minutes=(new_duration)
    @duration = (new_duration*60).to_i
  end

  def to_s
    "Song: #@name -- #@artist (#@duration)"
  end
  def play
    @plays += 1
    @@plays += 1
    "This song: #@plays play. Total #@@plays play."
  end

  def play
    @plays += 1
    @@plays += 1
    "This song: #@plays plays. Total #@@plays plays."
  end

end

class SongList
  MAX_TIME = 5*60
  def SongList.is_too_long(song)
    return song.duration > MAX_TIME
  end
end

class KaraokeSong < Song

  def initialize(name, artist, duration, lyrics)
    super(name, artist, duration)
    @lyrics = lyrics
  end

  def to_s
#    puts "Song: #@name -- #@artist (#@duration) [#@lyrics]"
    super + " [#@lyrics]"
  end

end

class SongList
  MAX_TIME = 5*60

  def SongList.is_too_long(song)
    return song.duration > MAX_TIME
  end

end

class MyLogger
  private_class_method :new
  @@logger = nil
  def MyLogger.create
    @@logger = new unless @@logger
    @@logger
  end

end

class Shape

  def initialize(num_sides, perimeter)
    @num_sides = num_sides
    @perimeter = perimeter
  end

  def Shape.triangle(side_length)
    Shape.new(3, side_length*3)
  end

  def Shape.square(side_length)
    Shape.new(4, side_length*4)
  end

end

song = Song.new("Bicyclops", "Fleck", 260)
puts song.inspect
puts song.to_s

new_song = KaraokeSong.new("My Way", "Sinatra", 255, "And now, the ...")
puts new_song.to_s

puts song.name
puts song.artist
puts song.duration

song.duration = 300
puts song.duration

song.name = "lifulei"
puts song.name

puts song.duration_in_minutes

song.duration_in_minutes = 6
puts song.duration
puts song.duration_in_minutes

s1 = Song.new("Song1", "Artist1", 100)
s2 = Song.new("Song2", "Artist2", 400)

puts s1.play
puts s2.play
puts s1.play

puts SongList.is_too_long(s1)
puts SongList.is_too_long(s2)

puts MyLogger.create.object_id
puts MyLogger.create.object_id
puts MyLogger.create.object_id

person = "Tim"
puts person.object_id
puts person.class
puts person

a = [1, 3, 5, 7, 9]
b = %w[2 4 6 d e f g]
puts a[-1]
puts a[-2]
a[2,2] = 'cat'
a[2,0] = 'dog'
a[1,1] = [9, 8, 7]
print a, "\n"
print b, "\n"

h = {'dog' => 'canine', 'cat' => 'feline', 'donkey' => 'asinine'}
h['cow'] = 'bovine'
h[12] = 'dodecine'
h['cat'] = 99
print h, "\n"
puts h.length
puts h['dog']
puts h[12] = 'dodecine'