Forum: Ruby "Unflattening" arrays

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Farrel L. (Guest)
on 2006-03-27 23:59
(Received via mailing list)
Hi folks,

Is there an easy way to get [1,2,3,4,5,6,7,8] into
[[1,2],[3,4],[5,6],[7,9]] or [[1,2,3,4],[5,6,7,8]] depending on a
parameter?

Farrel
Daniel H. (Guest)
on 2006-03-28 00:08
(Received via mailing list)
On Mar 27, 2006, at 9:59 PM, Farrel L. wrote:

> Is there an easy way to get [1,2,3,4,5,6,7,8] into
> [[1,2],[3,4],[5,6],[7,9]] or [[1,2,3,4],[5,6,7,8]] depending on a
> parameter?

require 'enumerator'

[1,2,3,4,5,6,7,8].enum_for(:each_slice, 4).to_a # -> [[1, 2, 3, 4],
[5, 6, 7, 8]]

-- Daniel
Sylvain J. (Guest)
on 2006-03-28 00:09
(Received via mailing list)
Check Enumerable#each_slice

require 'enumerator'
[1,2,3,4,5,6,7,8].enum_for(:each_slice, 2).to_a
Matthew M. (Guest)
on 2006-03-28 00:10
(Received via mailing list)
require 'enumerator'

> a = []
> (1..8).to_a.each_slice(2) { |x| a << x }
> p a
=> [[1, 2], [3, 4], [5, 6], [7, 8]]
Farrel L. (Guest)
on 2006-03-28 00:26
(Received via mailing list)
On 3/27/06, Daniel H. <removed_email_address@domain.invalid> wrote:

> [1,2,3,4,5,6,7,8].enum_for(:each_slice, 4).to_a # -> [[1, 2, 3, 4],
> [5, 6, 7, 8]]
>
> -- Daniel

This is just what I need. Thanks!
Andrew J. (Guest)
on 2006-03-28 00:29
(Received via mailing list)
On Tue, 28 Mar 2006 04:59:00 +0900, Farrel L.
<removed_email_address@domain.invalid>
wrote:

> Hi folks,
>
> Is there an easy way to get [1,2,3,4,5,6,7,8] into
> [[1,2],[3,4],[5,6],[7,9]] or [[1,2,3,4],[5,6,7,8]] depending on a
> parameter?

From 'enumerator.rb' , #each_slice(n) lets you iterate over successive
slices, and #enum_slice(n) generates an enumerator which you can use
the #to_a on to get the array of slices:

   require 'enumerator'
   a = [1,2,3,4,5,6,7,8,9]
   a.enum_slice(2).to_a   # => [[1, 2], [3, 4], [5, 6], [7, 8], [9]]
   a.enum_slice(4).to_a   # => [[1, 2, 3, 4], [5, 6, 7, 8], [9]]

andrew
William J. (Guest)
on 2006-03-28 00:59
(Received via mailing list)
Farrel L. wrote:
> Hi folks,
>
> Is there an easy way to get [1,2,3,4,5,6,7,8] into
> [[1,2],[3,4],[5,6],[7,9]] or [[1,2,3,4],[5,6,7,8]] depending on a
> parameter?
>
> Farrel

[1,2,3,4,5,6,7,8].inject([[]]){|a,x|
  a.last.size==2 ? a << [x] : a.last << x ; a }
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