Creating an Array: Difference between revisions

=={{header|Ruby}}==

This is the most basic way to create an empty one-dimensional array in Ruby:

<lang ruby> my_array = Array.new

another_array = []</lang>

Arrays of strings:

<lang>x = ['an', 'array', 'of', 'strings']

y = %w{another array of strings without the punctuation}</lang>

Ruby treats comma separated values on the right hand side of assignment as array. You could optionally surround the list with square brackets

<lang ruby> my_array = 1, 2, 3, 4, 5

my_array = [ 1, 2, 3, 4, 5 ]

array = [

[0, 0, 0, 0, 0, 0],

[1, 1, 1, 1, 1, 1],

[2, 2, 2, 2, 2, 2],

[3, 3, 3, 3, 3, 3]

]</lang>

You would call the array by this code. This will call the 4th element on the second list

<lang ruby>array[1][3]</lang>

We have to be careful when creating multidimensional arrays:

<lang ruby>a = [[0] * 3] * 2] # [[0, 0, 0], [0, 0, 0]]

a[0][0] = 1

puts a.inspect # [[1, 0, 0], [1, 0, 0]]</lang>

So both inner arrays refer to the same object

<lang ruby>a[0].equal? a[1] # true</lang>

The better way to create a multidimensional array is to use the form of <tt>Array.new</tt> that takes a block:

<lang ruby>a = Array.new(2) {Array.new(3) {0}}

puts a.inspect # [[0, 0, 0], [0, 0, 0]]

a[1][1] = 1

puts a.inspect # [[0, 0, 0], [0, 1, 0]]</lang>

You can also create a sequential array from a range using the 'splat' operator:

<lang ruby> array = [*0..3]

# or use the .to_a method for Ranges

array = (0..3).to_a #=> [0,1,2,3]</lang>

This lets us create [[0, 0, 0, 0, 0, 0], [1, 1, 1, 1, 1, 1], [2, 2, 2, 2, 2, 2], [3, 3, 3, 3, 3, 3]] programmatically:

<lang ruby> array = [*0..3].map {|i| [i] * 6}

array = 4.times.map {|i| Array.new(6,i)}

array = Array.new(4) {|i| Array.new(6,i)}</lang>