Things that I learned about Ruby Array

Copying Ruby Array

ruby-1.9.2-p290 :032 > a = [ [1,2], [3,4] ]
 => [[1, 2], [3, 4]] 
ruby-1.9.2-p290 :033 > b = a.dup
 => [[1, 2], [3, 4]] 
ruby-1.9.2-p290 :034 > c = a.clone
 => [[1, 2], [3, 4]] 
ruby-1.9.2-p290 :035 > d = Array.new(a)
 => [[1, 2], [3, 4]] 
ruby-1.9.2-p290 :036 > a[0][0] = 100
 => 100 
ruby-1.9.2-p290 :037 > a[0][1] = 100
 => 100 
ruby-1.9.2-p290 :038 > p a
[[100, 100], [3, 4]]
 => [[100, 100], [3, 4]] 
ruby-1.9.2-p290 :039 > p b
[[100, 100], [3, 4]]
 => [[100, 100], [3, 4]] 
ruby-1.9.2-p290 :040 > p c
[[100, 100], [3, 4]]
 => [[100, 100], [3, 4]] 
ruby-1.9.2-p290 :041 > p d
[[100, 100], [3, 4]]
 => [[100, 100], [3, 4]] 
ruby-1.9.2-p290 :042 > a[0].object_id 
 => 2152634120 
ruby-1.9.2-p290 :043 > b[0].object_id
 => 2152634120 
ruby-1.9.2-p290 :044 > c[0].object_id
 => 2152634120 
ruby-1.9.2-p290 :045 > d[0].object_id
 => 2152634120