Access

One can access individual items in an array by appending to the array another set of square brackets enclosing the desired index. [] is a method that can use a special syntax. Try accessing array elements for yourself!

got_characters = ["Robb", "Sansa", "Arya", "Bran", "Rickon"]
got_characters[0]  # => "Robb" # got_characters.[](0) is equivalent but uglier
got_characters[3]  # => "Bran"
got_characters[20] # => nil (nothing exists at this index)

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Arrays are zero-indexed, i.e., the first element of the array is at the zeroth index. In the above example, the string "Robb" is the first element and therefore, the zeroth index. The second element of the array is at the first index. "Sansa", the second element, is at the first index.

One can also access array elements using negative indices. The last element of the array is at the -1 index, the penultimate is at -2, etc. With negative indices, you essentially start at the end of the array and work your way backward.

got_characters = ["Robb", "Sansa", "Arya", "Bran", "Rickon"]
last = got_characters[-1] #=> "Rickon"
third_to_last = got_characters[-3] #=> "Arya"

last + " " + third_to_last #=> "Rickon Arya"

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One can access multiple elements in an array by using ranges instead of single indices. Doing so returns another array.

got_characters = ["Robb", "Sansa", "Arya", "Bran", "Rickon"]
got_characters[0..2] #=> ["Robb", "Sansa", "Arya"]
got_characters[0...-1] #=> ["Robb", "Sansa", "Arya", "Bran"]

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0..2 is a range object, another data structure. The two dots indicate that the range is inclusive, i.e., the range comprises all integers from 0 to 2, including 2. Three dots indicate an exclusive range: 0...11 is equivalent to 0..10. One can also declare a range of characters (e.g., "a".."c", "A"..."D"). One can type convert a range to an array using the to_a method:

(0..3).to_a #=> [0,1,2,3]
("A"..."D").to_a #=> ["A", "B", "C"]

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Although the range 0...-1 in got_characters[0...-1] is technically empty, when using a range in array access, -1 is equivalent to the array's length minus one.

got_characters = ["Robb", "Sansa", "Arya", "Bran", "Rickon"]
got_characters[0...-1] == got_characters[0...(got_characters.length - 1)] #=> true

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Ruby provides idiomatic methods for accessing the first and last elements of arrays:

got_characters = ["Robb", "Sansa", "Arya", "Bran", "Rickon"]
got_characters.first #=> "Robb"
got_characters.last #=> "Rickon"

Try running the code. (Click the run button.)