Enumberable and Sets

2.1.5 :011 > 'begin' <=> 'end'
 => -1 
2.1.5 :012 > 'same' <=> 'same'
 => 0 
2.1.5 :013 > a = [5, 3, 4, 1]
 => [5, 3, 4, 1] 
2.1.5 :014 > a.sort
 => [1, 3, 4, 5] 
2.1.5 :015 > a.any? {|i| i > 6}
 => false 
2.1.5 :016 > a.any? {|i| i > 4}
 => true 
2.1.5 :017 > a.all? {|i| i > 4}
 => false 
2.1.5 :018 > a.all? {|i| i > 0}
 => true 
2.1.5 :019 > a.collect {|i| i * 2} 
 => [10, 6, 8, 2] 
2.1.5 :020 > a.select {|i| i % 2 == 0} # even
 => [4] 
2.1.5 :021 > a.select {|i| i % 2 == 1} # odd 
 => [5, 3, 1] 
2.1.5 :022 > a.max
 => 5 
2.1.5 :023 > a.member?(2)
 => false 
2.1.5 :024 > a.inject {|sum_code_block, i| sum_code_block + i}
 => 13 
2.1.5 :025 > a.inject {|product_code_block, i| product_code_block * i}
 => 60