Delete array element within iterator block?

Ruby
1

How do I (in an elegant way) delete an element of an array within a
block, while using a block iterator?

The code below won’t work (the wanted behavior here is to get all array
elements to print and but also delete the 2nd element after it has been
encountered):

arr = [1,2,3,4]
arr.each_with_index { |e, i|
p e
arr.delete_at(i) if i == 1
}

results in:
1
2
4

Of curse, I could loop and keep track of the index manually, but I’m
mainly checking if there is any built-in stuff here.

Best regards,

Jari W.

2

On 30/11/2007, at 10:51 PM, Jari W. wrote:

How do I (in an elegant way) delete an element of an array within a
block, while using a block iterator?
I assume using delete_if is no good in this situation?
[1,2,3,4,5,6].delete_if{|i| i>4}
[1,2,3,4]

}

results in:
1
2
4
This is interesting, because although the results printed on the
screen imply the 3 was removed, if you look at the array afterthe
operation you’ll see it was the 2 removed (as we wanted)

irb(main):013:0> (a=[1,2,3,4]).each_with_index{|e,i| p
e;a.delete_at(i) if i==1}
1
2
4
=> [1, 3, 4]

I’ve no ideas why

Cheers,
Dave

3

HI –

On Fri, 30 Nov 2007, Sharon P. wrote:

results in:
2
4
=> [1, 3, 4]

I’ve no ideas why

First time through:

a => [1,2,3,4]
e => 1
i => 0

Second time through:

a => [1,2,3,4]
e => 2
i => 1

Third time through:

a => [1,3,4]
e => 4 # i.e., a[2]
i => 2

Or some such thing. Of course the best idea is never to do this :slight_smile:

David

4

Sharon P. wrote:

On 30/11/2007, at 10:51 PM, Jari W. wrote:

How do I (in an elegant way) delete an element of an array within a
block, while using a block iterator?
I assume using delete_if is no good in this situation?
[1,2,3,4,5,6].delete_if{|i| i>4}
[1,2,3,4]

Thanks, delete_if works just fine!

Best regards,

Jari W.