Grouping elements of an array?

ruby-talk
1

Hello,

What's the best way to do the following?

[1,2,3,4,5,6,7,8,9] => [[1,2,3],[4,5,6],[7,8,9]]

I want to transform the array into an array of arrays with fixed number
of elements.
I think there should be a method but I can't find it.

I can iterate the elements using a counter to divide but it's so
boring.

Thanks in advance.

Sam

2

class Array
  def group_in(how_many)
   ret_array =
   new_array =
   self.each {|elem| how_many.times { new_array << self.shift };
ret_array << new_array; new_array = ; }
   ret_array
  end
end

x = [1,2,3,4,5,6,7,8,9]
x = x.group_in(3)
require 'pp'
pp x

[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

That should do it. :slight_smile: Not sure if it's the best way, but it will work.

--Jeremy

···

On 1/8/07, Sam Kong <sam.s.kong@gmail.com> wrote:

Hello,

What's the best way to do the following?

[1,2,3,4,5,6,7,8,9] => [[1,2,3],[4,5,6],[7,8,9]]

I want to transform the array into an array of arrays with fixed number
of elements.
I think there should be a method but I can't find it.

I can iterate the elements using a counter to divide but it's so
boring.

Thanks in advance.

Sam

--
My free Ruby e-book:
http://www.humblelittlerubybook.com/book/

My blogs:

http://www.rubyinpractice.com/

3

requre 'enumerator'

[1,2,3,4,5,6,7,8,9].enum_slice(3).inject(){|array,slice| array << slice}

Farrel

···

On 08/01/07, Sam Kong <sam.s.kong@gmail.com> wrote:

Hello,

What's the best way to do the following?

[1,2,3,4,5,6,7,8,9] => [[1,2,3],[4,5,6],[7,8,9]]

I want to transform the array into an array of arrays with fixed number
of elements.
I think there should be a method but I can't find it.

I can iterate the elements using a counter to divide but it's so
boring.

Thanks in advance.

Sam

4

FYI. B is what you expect:
A=[1,2,3,4,5,6,7,8,9];B=;
3.times {B<<A.slice!(0..2);}

Sam Kong wrote:

···

Hello,

What's the best way to do the following?

[1,2,3,4,5,6,7,8,9] => [[1,2,3],[4,5,6],[7,8,9]]

I want to transform the array into an array of arrays with fixed number
of elements.
I think there should be a method but I can't find it.

I can iterate the elements using a counter to divide but it's so
boring.

Thanks in advance.

Sam

5

Farrel Lifson wrote:

What's the best way to do the following?

[1,2,3,4,5,6,7,8,9] => [[1,2,3],[4,5,6],[7,8,9]]

...

[1,2,3,4,5,6,7,8,9].enum_slice(3).inject(){|array,slice| array << slice}

Alternately,

[1,2,3,4,5,6,7,8,9].enum_for(:each_slice,3).to_a
=> [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

···

On 08/01/07, Sam Kong <sam.s.kong@gmail.com> wrote:

--
        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

6

Farrel Lifson wrote:

···

On 08/01/07, Sam Kong <sam.s.kong@gmail.com> wrote:
> Hello,
>
> What's the best way to do the following?
>
> [1,2,3,4,5,6,7,8,9] => [[1,2,3],[4,5,6],[7,8,9]]
>
> I want to transform the array into an array of arrays with fixed number
> of elements.
> I think there should be a method but I can't find it.
>
> I can iterate the elements using a counter to divide but it's so
> boring.
>
> Thanks in advance.
>
> Sam
>
>
>

requre 'enumerator'

[1,2,3,4,5,6,7,8,9].enum_slice(3).inject(){|array,slice| array << slice}

Farrel

requre 'enumerator'
[ 1, 2, 3, 4, 5, 6, 7, 8 ].enum_slice(3).to_aj

Without "require":
[ 1, 2, 3, 4, 5, 6, 7, 8 ].inject([]){|a,e|
  a << if a.last.size==3; a.last << e; a}

7

Hi William,

William James wrote:

Without "require":
[ 1, 2, 3, 4, 5, 6, 7, 8 ].inject([]){|a,e|
  a << if a.last.size==3; a.last << e; a}

This looks really clever.
I like it.

Sam