irb(main):001:0> a = [ 3.14159, "pie", 99 ]
=> [3.14159, "pie", 99]
irb(main):003:0> a.length
=> 3
irb(main):004:0> b = Array.new
=> []
irb(main):006:0> b.length
=> 0
irb(main):007:0> a = [ 1, 3, 5, 7, 9 ]
=> [1, 3, 5, 7, 9]
irb(main):008:0> a[-1]
=> 9
irb(main):009:0> a[-2]
=> 7
irb(main):010:0> a[-99]
=> nil
irb(main):011:0> a[1, 3]
=> [3, 5, 7]
irb(main):012:0> a[3, 1]
=> [7]
irb(main):013:0> a[-3, 2]
=> [5, 7]
irb(main):014:0> a[1..3]
=> [3, 5, 7]
irb(main):015:0> a[1...3]
=> [3, 5]
irb(main):016:0> a[3..3]
=> [7]
irb(main):017:0> a[-3..-1]
=> [5, 7, 9]
irb(main):018:0>irb(main):001:0> a = [ 1, 3, 5, 7, 9 ]
=> [1, 3, 5, 7, 9]
irb(main):002:0> a[1] = 'bat'
=> "bat"
irb(main):003:0> a
=> [1, "bat", 5, 7, 9]
irb(main):004:0> a[3] = [ 9, 8 ]
=> [9, 8]
irb(main):005:0> a
=> [1, "bat", 5, [9, 8], 9]
irb(main):006:0> a[6] = 99
=> 99
irb(main):007:0> a
=> [1, "bat", 5, [9, 8], 9, nil, 99]
irb(main):008:0>
irb(main):001:0> a = [ 1, 3, 5, 7, 9 ]
=> [1, 3, 5, 7, 9]
irb(main):002:0> a[2, 2] = 'cat'
=> "cat"
irb(main):003:0> a
=> [1, 3, "cat", 9]
irb(main):004:0> a[2, 0] = 'dog'
=> "dog"
irb(main):005:0> a
=> [1, 3, "dog", "cat", 9]
irb(main):006:0> a[1, 1] = [ 9, 8, 7 ]
=> [9, 8, 7]
irb(main):007:0> a
=> [1, 9, 8, 7, "dog", "cat", 9]
irb(main):008:0> a[0..3] = []
=> []
irb(main):009:0> a
=> ["dog", "cat", 9]
irb(main):010:0> a[5] = 99
=> 99
irb(main):011:0> a
=> ["dog", "cat", 9, nil, nil, 99]
irb(main):012:0>
