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HI

I am a novice in Ruby programming so this question might look trivial
to lot of people.

But I am struggling to copy an array.

I am using

a = []
b = a

/* some manipulation here on "b" and "a" I havent touched at all*/

Here when i am trying to see contents of "a" and "b" both have same
contents

But my expectation was they shud be different

Instead of b = a, I also tried b.replace(a)

but no luck here also.

Please help me on how to make a duplicate("b") of "a" so that changes
done on b will not affect a

Thanks
Pikender Sharma

On Fri, Nov 13, 2009 at 2:30 PM, PIKI <> wrote:

> But I am struggling to copy an array.
>
> I am using
>
> a = []
> b = a
>
> /* some manipulation here on "b" and "a" I havent touched at all*/
>
> Here when i am trying to see contents of "a" and "b" both have same
> contents
>
> But my expectation was they shud be different
>
> Instead of b = a, I also tried b.replace(a)
>
> but no luck here also.
>
> Please help me on how to make a duplicate("b") of "a" so that changes
> done on b will not affect a

irb(main):001:0> a = [1,2,3,4]
=> [1, 2, 3, 4]
irb(main):002:0> b = a.dup
=> [1, 2, 3, 4]
irb(main):003:0> b[0] = 55
=> 55
irb(main):004:0> a
=> [1, 2, 3, 4]
irb(main):005:0> b
=> [55, 2, 3, 4]

Hope this helps,

Jesus.

On Nov 13, 6:34*pm, Jesús Gabriel y Galán <jgabrielyga...@gmail.com>
wrote:
> On Fri, Nov 13, 2009 at 2:30 PM, PIKI <avid.p...@gmail.com> wrote:
> > But I am struggling tocopyanarray.
>
> > I am using
>
> > a = []
> > b = a
>
> > /* some manipulation here on "b" and "a" I havent touched at all*/
>
> > Here when i am trying to see contents of "a" and "b" both have same
> > contents
>
> > But my expectation was they shud be different
>
> > Instead of b = a, I also tried b.replace(a)
>
> > but no luck here also.
>
> > Please help me on how to make a duplicate("b") of "a" so that changes
> > done on b will not affect a
>
> irb(main):001:0> a = [1,2,3,4]
> => [1, 2, 3, 4]
> irb(main):002:0> b = a.dup
> => [1, 2, 3, 4]
> irb(main):003:0> b[0] = 55
> => 55
> irb(main):004:0> a
> => [1, 2, 3, 4]
> irb(main):005:0> b
> => [55, 2, 3, 4]
>
> Hope this helps,
>
> Jesus.- Hide quoted text -
>
> - Show quoted text -

Hi Jesús Gabriel y Galán

Thanks for the reply and help

I tried ur solution but it is also not working

I am unable to figure out the trick

Thanks
Pikender Sharma

> I tried ur solution but it is also not working
>
> I am unable to figure out the trick

In order to help us to figure out what is the problem, you might want
to post a code snippet demonstrating the defect and explain what how
you would expect ruby to behave.

Array#dup creates a copy of the array, not of the elements in the
array, aka a shallow copy.

l> Array#dup creates a copy of the array, not of the elements in the
l> array, aka a shallow copy.

Is there a way to make a deep copy? That is ... in the code below,
could b.dup be replaced with something like b.deepdup?


irb(main):019:0> a1 = [1,2,3,4]
=> [1, 2, 3, 4]
irb(main):020:0> b = [a1,5]
=> [[1, 2, 3, 4], 5]
irb(main):021:0> c1 = b
=> [[1, 2, 3, 4], 5]
irb(main):022:0> c2 = b.dup
=> [[1, 2, 3, 4], 5]
irb(main):023:0> a1[0] = "hi"
=> "hi"
irb(main):024:0> a1
=> ["hi", 2, 3, 4]
irb(main):025:0> c1
=> [["hi", 2, 3, 4], 5]
irb(main):026:0> c2
# because of the shallow copy, c2[0][0] is "hi" instead of a naively
# assumed 1.
=> [["hi", 2, 3, 4], 5]
irb(main):027:0> c1[1] = "bye"
=> "bye"
irb(main):028:0> c1
=> [["hi", 2, 3, 4], "bye"]
irb(main):029:0> c2
# The shallow copy gives the expected result for c2[1], below.
=> [["hi", 2, 3, 4], 5]

you can make it via this method "clone" b =3D a.clone
Am 14.11.2009 um 11:25 schrieb PIKI:

> On Nov 13, 6:34 pm, Jes=FAs Gabriel y Gal=E1n =
<jgabrielyga...@gmail.com>
> wrote:
>> On Fri, Nov 13, 2009 at 2:30 PM, PIKI <avid.p...@gmail.com> wrote:
>>> But I am struggling tocopyanarray.
>>
>>> I am using
>>
>>> a =3D []
>>> b =3D a
>>
>>> /* some manipulation here on "b" and "a" I havent touched at all*/
>>
>>> Here when i am trying to see contents of "a" and "b" both have same
>>> contents
>>
>>> But my expectation was they shud be different
>>
>>> Instead of b =3D a, I also tried b.replace(a)
>>
>>> but no luck here also.
>>
>>> Please help me on how to make a duplicate("b") of "a" so that =20
>>> changes
>>> done on b will not affect a
>>
>> irb(main):001:0> a =3D [1,2,3,4]
>> =3D> [1, 2, 3, 4]
>> irb(main):002:0> b =3D a.dup
>> =3D> [1, 2, 3, 4]
>> irb(main):003:0> b[0] =3D 55
>> =3D> 55
>> irb(main):004:0> a
>> =3D> [1, 2, 3, 4]
>> irb(main):005:0> b
>> =3D> [55, 2, 3, 4]
>>
>> Hope this helps,
>>
>> Jesus.- Hide quoted text -
>>
>> - Show quoted text -
>
> Hi Jes=FAs Gabriel y Gal=E1n
>
> Thanks for the reply and help
>
> I tried ur solution but it is also not working
>
> I am unable to figure out the trick
>
> Thanks
> Pikender Sharma
>