Can somebody please tell me how to declare a new instance of a 2-dimensional array? Most of the languages use something like:
array = Array.new[2][2]
I don't know how to do it in Ruby.
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2That would be quite tedious if he wanted the height and width to be 1000, for example.Mike Lewis– Mike Lewis2011-03-21 00:57:30 +00:00Commented Mar 21, 2011 at 0:57
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5 Answers
You can do:
width = 2
height = 3
Array.new(height){Array.new(width)} #=> [[nil, nil], [nil, nil], [nil, nil]]
1 Comment
Kevin Wheeler
Traditionally arrays are layed out in row major order, ie
[row, row row]. So your example should swap height and width so that it's like this: Array.new(height){Array.new(width)}. That way you can access an element using arrayInstance[row][column] instead of arrayInstance[column][row]To declare 2d array in ruby, Use following syntax with initialization value
row, col, default_value = 5, 4, 0
arr_2d = Array.new(row){Array.new(col,default_value)}
=> [[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0]]
We can do any level of nesting, like for 3d array(5 x 4 x 2): you can pass block to initialize array in most inner Array
z = 2
arr_3d = Array.new(row){Array.new(col){Array.new(z){|index| index}}}
=> [[[0, 1], [0, 1], [0, 1], [0, 1]],
[[0, 1], [0, 1], [0, 1], [0, 1]],
[[0, 1], [0, 1], [0, 1], [0, 1]],
[[0, 1], [0, 1], [0, 1], [0, 1]],
[[0, 1], [0, 1], [0, 1], [0, 1]]]
Now, you can access its element using [] operator like arr_2d[0][1], actually its array of arrays
2 Comments
calasyr
Didn't know you could specify a default element for an array. So you can specify the inner array as the default for the outer array too: s = Array.new(3, Array.new(3, true)) => [[true, true, true], [true, true, true], [true, true, true]] Oh, no, you can't. The same array is used for each row. Fail.
aqfaridi
Use {} instead of () while declaring the inner array, it will work
You could also initialize passing a value:
Array.new(3) { Array.new(3) { '0' } }
Output:
[
["0", "0", "0"],
["0", "0", "0"],
["0", "0", "0"]
]
Comments
You can declare a multidimensional array in Ruby with:
Array.new(Number_of_ROWs){Array.new(Number_of_COLUMNs)}
How To Use This Syntax
Let us understand it by using above example i.e. array = Array.new[2][2].
So, in this example we've to declare an empty multidimensional array with 2 rows and 2 column.
Let us start implementing the our syntax now,
array = Array.new(2){Array.new(2)}
Now you've an array with 2 rows and 2 column with nil values.
Now the array variable contains [[nil, nil], [nil, nil]] which is consider as an empty multidimensional array or nil value multidimensional array.
Comments
simply: array = Array.new(8,Array.new(8))
1 Comment
Mark Kuczmarski
This doesn't really work. This would create 8 copies of the same array, but not 8 distinct arrays