ruby哈希表

irb(main):001:0> h = { 'dog' => 'canine', 'cat' => 'feline', 'donkey' => 'asinine' }
=> {"cat"=>"feline", "donkey"=>"asinine", "dog"=>"canine"}
irb(main):002:0> h.length
=> 3
irb(main):003:0> h['dog']
=> "canine"
irb(main):004:0> h['cow'] = 'bovine'
=> "bovine"
irb(main):005:0> h
=> {"cow"=>"bovine", "cat"=>"feline", "donkey"=>"asinine", "dog"=>"canine"}
irb(main):008:0> h[12]    = 'dodecine'
=> "dodecine"
irb(main):009:0> h
=> {"cow"=>"bovine", "cat"=>"feline", 12=>"dodecine", "donkey"=>"asinine", "dog"=>"canine"}
irb(main):010:0> h['cat'] = 99
=> 99
irb(main):011:0> h
=> {"cow"=>"bovine", "cat"=>99, 12=>"dodecine", "donkey"=>"asinine", "dog"=>"canine"}
irb(main):012:0>