But for users the following might be surprising: If a user defines
deepcopy(::T) for a user defined type T and x is of type Array{T, 1}, then
deepcopy(x) is not the "same" as [ deepcopy(z) for z in x]. At least this
is my experience and how I understand deepcopy.jl.
On Sunday, August 14, 2016 at 8:31:20 PM UTC+2, Cedric St-Jean wrote:
>
> instead, it puts the same object (which is a copy) in the first and third
>> positions and you get the same behavior. Maybe this is not the intended
>> behavior of deepcopy?
>>
>
> It's intentional. deepcopy has to keep and update a dictionary as it
> traverses the datastructure in order to provide the behaviour. Without it,
> it would be impossible to copy cyclic data-structures, as the recursive
> traversal would never end.
>
> On Sunday, August 14, 2016 at 11:36:04 AM UTC-4, Tommy Hofmann wrote:
>>
>> Indeed, the behavior of deepcopy with respect to arrays of user defined
>> types is surprising.
>>
>> If you define
>>
>> Base.deepcopy_internal(x::MyType, ::ObjectIdDict) = MyType(deepcopy(x.a))
>>
>> then deepcopy(MyType_Vec[[1, 3, 1]]) gives a new object with
>> "independent" elements. See also
>> http://docs.julialang.org/en/release-0.4/stdlib/base/#Base.deepcopy
>>
>>
>> On Friday, August 12, 2016 at 8:56:32 PM UTC+2, Josh Langsfeld wrote:
>>>
>>> For your second question, I would have expected just doing
>>> deepcopy(MyType_Vec[[1,3,1]]) would have created a new array with a new
>>> object allocated for each element. Instead, it puts the same object (which
>>> is a copy) in the first and third positions and you get the same behavior.
>>> Maybe this is not the intended behavior of deepcopy?
>>>
>>> You can easily get around though this by explicitly calling deepcopy on
>>> each element directly: MyType_Vec = map(deepcopy, MyType_Vec[[1,3,1]]).
>>> A similar alternative with an array comprehension would be: MyType_Vec
>>> = [deepcopy(MyType_Vec[i]) for i in [1,3,1]].
>>>
>>> (an array comprehension also answers your first question: MyType_Vec =
>>> [MyType([0.0]) for i=1:3])
>>>
>>> On Friday, August 12, 2016 at 11:47:39 AM UTC-4, Jan wrote:
>>>
>>> I have a beginner question for which I cannot find the answer after
>>>> quite some searching.
>>>>
>>>>
>>>> type MyType
>>>> a::Array{Float64,1}
>>>> end
>>>>
>>>> # Fill an array with "independent" instances of MyType. (By the way,
>>>> is there a shorter way to do this?)
>>>>
>>>> MyType_Vec = Array(MyType, 3);
>>>>
>>>> for i in eachindex(MyType_Vec)
>>>>
>>>> MyType_Vec[i] = MyType([0.0]);
>>>>
>>>> end
>>>>
>>>> MyType_Vec
>>>>
>>>> # Change the value of MyType_Vec[1].a[1] to 2.
>>>>
>>>> MyType_Vec[1].a[1] = 2;
>>>>
>>>> MyType_Vec
>>>>
>>>> # Shuffle the vector but with repeated elements
>>>>
>>>> MyType_Vec = MyType_Vec[[1,3,1]];
>>>>
>>>> # Change the value of MyType_Vec[1].a[1] to 4.
>>>>
>>>> MyType_Vec[1].a[1] = 4;
>>>>
>>>> MyType_Vec
>>>>
>>>> # The value of MyType_Vec[3].a[1] also changed to 4.
>>>>
>>>>
>>>> How can I avoid this reference behaviour? I want that, after the
>>>> shuffling step, the 3 elements of MyType_Vec should be "independent" so
>>>> that if I change MyType_Vec[1].a[1] nothing else is affected. I have
>>>> tried copy and deepcopy without success.
>>>>
>>>> I would be very happy if someone could help me out. I'm stuck...
>>>>
>>>> Many thanks in advance.
>>>>
>>>
>>>
>>
