non-copy slices

[Ajit Kumar]

On Thu, Nov 19, 2009 at 8:14 PM, Ethan Furman <ethan at stoneleaf.us> wrote:
>> No I'm well aware that there is no deep copy of the objects and the lists
>> only keep references to the objects and in essence they have the same
>> objects in there. But this doesn't mean they are the same list.
>> Modifications to slices are not written back to the original list.
>>
>> x = range(5)
>> y = x[1:3]
>> y[0] = 13
>> x[1] == y[0]  --> False
>>
>> Of course if I modify the object in the slice then the original list will
>> see the change, but this is not what I was saying. Second and more
>> importantly it's the performance penalty from allocating a large number of
>> lists produced from the slices and the copy of the references. islice does
>> not have this penalty, it should only instantiate a small object that
>> iterates on the original list.
>>
>> Themis
>
> So "shallow copy" == "new label created for existing object".
>
> So is your desired behavior to write back to the original list if your
> sub-list is modified?  In other words, you are creating a window onto an
> existing list?  If not, what would happen when a sublist element was
> modified (or deleted, or appended, or ...)?

On a related note, GO encourages use of slices.

http://golang.org/doc/effective_go.html#slices