Rubyのclone,dupはshallow copyなのではまる例

opy_test.rb

#!/usr/bin/ruby
#
# Rubyのclone,dupはshallow copyなのではまる例
# 完全な複製を作るときはMarshal.load(Marshal.dump(コピー対象))を使う
#
#   $ ruby copy_test.rb
#   == case 1 ==
#   [[[200, 201, 202], [210, 211, 212], [220, 221, 222]],
#    [[200, 201, 202], [210, 211, 212], [220, 221, 222]],
#    [[200, 201, 202], [210, 211, 212], [220, 221, 222]]]
#   == case 2 ==
#   [[[0, 1, 2], [10, 11, 12], [20, 21, 22]],
#    [[100, 101, 102], [110, 111, 112], [120, 121, 122]],
#    [[200, 201, 202], [210, 211, 212], [220, 221, 222]]]
#
require 'pp'

n = 3

puts "== case 1 =="
a = Array.new(n, 0)
b = Array.new(n){a.clone}
c = Array.new(n){b.clone}

(0...n).each{|z| 
  (0...n).each{|y| 
    (0...n).each{|x|
      c[z][y][x] = x + y * 10 + z * 100
    }
  }
}
pp c

puts "== case 2 =="
a = Array.new(n, 0)
b = Array.new(n){a.clone}
c = Array.new(n){Marshal.load(Marshal.dump(b))}

(0...n).each{|z| 
  (0...n).each{|y| 
    (0...n).each{|x|
      c[z][y][x] = x + y * 10 + z * 100
    }
  }
}
pp c