How can I copy an array and its elements? (call by value)

Hi all,

I’m failing at something really basic: copying an array and its
contents, so that I can modify the copy without modifying the original.

Here’s an example:

irb(main):006:0> a = [1, 2]
=> [1, 2]
irb(main):007:0> b = a
=> [1, 2]
irb(main):008:0> b.delete(1)
=> 1
irb(main):009:0> b
=> [2]
irb(main):010:0> a
=> [2]

I guess the problem is that arrays are called by name not by value, so
that ‘b’ copy points to the same adress in memory as ‘a’. How can I
create an independent copy of ‘a’?

Thanks,
Janus

Hello,

I’m failing at something really basic: copying an array and its
contents, so that I can modify the copy without modifying the original.

I think the method ‘dup’ is what you are looking for

irb(main):001:0> a = [1,2]
=> [1, 2]
irb(main):002:0> b = a.dup
=> [1, 2]
irb(main):003:0> b.delete(1)
=> 1
irb(main):004:0> b
=> [2]
irb(main):005:0> a
=> [1, 2]

Cheers,

Le Fri, 7 Aug 2009 10:18:52 -0500,
Janus B. [email protected] a écrit :

How can I create an independent copy of ‘a’?

b=a[0…-1]

Thank you both, that’s exactly what I’m looking for!

On 07.08.2009 17:47, Janus B. wrote:

Thank you both, that’s exactly what I’m looking for!

Just note that #dup and #clone do a shallow copy, so if you modify
objects in the copy this change will also be seen via the original
Array. Depending on what you do #map might be more appropriate.

Kind regards

robert

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