"Unflattening" arrays

ruby-talk
1

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

2

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

···

On Mar 27, 2006, at 9:59 PM, Farrel Lifson 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?

3

Check Enumerable#each_slice

require 'enumerator'
[1,2,3,4,5,6,7,8].enum_for(:each_slice, 2).to_a

···

--
Sylvain Joyeux

4

require 'enumerator'

a =
(1..8).to_a.each_slice(2) { |x| a << x }
p a

=> [[1, 2], [3, 4], [5, 6], [7, 8]]

5

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

···

On Tue, 28 Mar 2006 04:59:00 +0900, Farrel Lifson <farrel.lifson@gmail.com> 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?

--
Andrew L. Johnson http://www.siaris.net/
      What have you done to the cat? It looks half-dead.
          -- Schroedinger's wife

6

Farrel Lifson 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 << : a.last << x ; a }

7

This is just what I need. Thanks!

···

On 3/27/06, Daniel Harple <dharple@generalconsumption.org> 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