# FAQ: Data Structures - Arrays of Arrays

This community-built FAQ covers the “Arrays of Arrays” exercise from the lesson “Data Structures”.

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## FAQs on the exercise Arrays of Arrays

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Why is the multidimensional array 2 dimensional? There are 4 arrays within the example multidimensional array no?

The first thng we need to appreciate about arrays is their linearity. Arrays are linear in nature.

When the elements of an array are themselves arrays, it has no bearing on the linearity of the parent array. It’s an array of arrays. Arrays are not intended to emulate tables so there is no x by y dimensioning in their definition.

Hi everyone,
what does the “#” sign job in the code,
and how come you can use x and n
without declaring them
regarding this code

multi_d_array.each { |x| puts “#{x}\n” }

2 Likes

The `#` when paired up with `{}` signifies expression interpolation. Notice in your code it is written,

``````puts "#{x}\n"
``````

which literally means,

put string comprised of an expression containing the current value of `x` and a newline escape character.

3 Likes

thank you for your reply, and how did the “n” affected the output, and again without declaring it before

1 Like

Written as an escape sequence, `\n` inserts a newline character (line break) which when added to the one that `puts` inserts gives double line spacing.

3 Likes

multi_d_array = [[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0]]

multi_d_array.each { |x| puts “#{x}\n” }

Hi, could somebody please explain why we use { |x| puts “#{x}\n” }. I am a little confused

The `Array.each` method takes a block, the `{ }` which encloses the code that will run on each iteration of the array. `|x|` is called the block parameter, a variable local to the block which binds to one element in the array at a time. In the above, we puts that value to the display. `"#{x}\n"` is a string which employs interpolation of the variable’s value along with a newline character which when combined with the one Ruby inserts after every `puts` gives a blank line between each print out. `puts` is short for, `put string`.

Expected output

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

[0, 0, 0, 0]

[0, 0, 0, 0]

[0, 0, 0, 0]

``````
1 Like

why do I need to type
puts x