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You can create an array by listing some items within square brackets ([]) and separating them with commas. Ruby's arrays can accomodate diverse object types.

ruby> ary = [1, 2, "3"] [1, 2, "3"]

Arrays can be concatenated or repeated just as strings can.

ruby> ary + ["foo", "bar"] [1, 2, "3", "foo", "bar"] ruby> ary * 2 [1, 2, "3", 1, 2, "3"]

We can use index numbers to refer to any part of a array.

ruby> ary[0] 1 ruby> ary[0,2] [1, 2] ruby> ary[0..1] [1, 2] ruby> ary[-2] 2 ruby> ary[-2,2] [2, "3"] ruby> ary[-2..-1] [2, "3"]

(Negative indices mean offsets from the end of an array, rather than the beginning.)

Arrays can be converted to and from strings, using join and split respecitvely:

ruby> str = ary.join(":") "1:2:3" ruby> str.split(":") ["1", "2", "3"]

Hashes

An associative array has elements that are accessed not by sequential index numbers, but by keys which can have any sort of value. Such an array is sometimes called a hash or dictionary; in the ruby world, we prefer the term hash. A hash can be constructed by quoting pairs of items within curly braces ({}). You use a key to find something in a hash, much as you use an index to find something in an array.

ruby> h = {1 => 2, "2" => "4"} {1=>2, "2"=>"4"} ruby> h[1] 2 ruby> h["2"] "4" ruby> h[5] nil ruby> h[5] = 10 # appending value 10 ruby> h {5=>10, 1=>2, "2"=>"4"} ruby> h.delete 1 # deleting value 2 ruby> h[1] nil ruby> h {5=>10, "2"=>"4"}

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