Velocity Reviews > Ruby > Multi-dimensional arrays

Multi-dimensional arrays

Graham Smith
Guest
Posts: n/a

 07-07-2006
Hi,

I have just started programming with Ruby and have run into the following
problem.

I'm trying to work with 3 dimensional arrays and have run into a problem
dimensioning the array.

a = [[[]]]
a[0][0] = [ 0,1,2,3]
a[0][1] = [ "zero", "one","two",three"]

The above assignments work without a problem, but the following assignment
fails.

a[1][0] = [ 4, 5, 6, 7]
NoMethodError: undefined method `[]=' for nil:NilClass

How do you dimension the number of elements in a multi-dimensional array when
the final number of elements in the array is not known.

--
Regards,

Graham Smith

Jake McArthur
Guest
Posts: n/a

 07-07-2006
On Jul 7, 2006, at 12:09 PM, Graham Smith wrote:

> How do you dimension the number of elements in a multi-dimensional
> array when
> the final number of elements in the array is not known.

Try http://raa.ruby-lang.org/project/narray/

- Jake McArthur

Logan Capaldo
Guest
Posts: n/a

 07-08-2006

On Jul 7, 2006, at 1:09 PM, Graham Smith wrote:

> Hi,
>
> I have just started programming with Ruby and have run into the
> following
> problem.
>
> I'm trying to work with 3 dimensional arrays and have run into a
> problem
> dimensioning the array.
>
> a = [[[]]]
> a[0][0] = [ 0,1,2,3]
> a[0][1] = [ "zero", "one","two",three"]
>
> The above assignments work without a problem, but the following
> assignment
> fails.
>
> a[1][0] = [ 4, 5, 6, 7]
> NoMethodError: undefined method `[]=' for nil:NilClass
>
> How do you dimension the number of elements in a multi-dimensional
> array when
> the final number of elements in the array is not known.
>
> --
> Regards,
>
> Graham Smith
>

class Array
def default(&proc)
@default = proc
self
end

alias_method :rb_array_indexing, :"[]"
def [](index)
if @default and index.kind_of? Integer and index >= length
index.downto(length) do |i|
self[i] = @default.call(i)
end
end
rb_array_indexing(index)
end
end

a = []
a.default { [] }

a[1][0] = "Hello"
a #=> [[], ["Hello"]]