OK, I now see that I misunderstood the question. After rereading it, I
noticed something important. I think your deepcopy_internal version is
broken, but you did not notice it since you did _not_ define
Base.deepcopy_internal(::SelfReferential, ::ObjectIdDict).
You should do the following:
import Base: deepcopy_internal
type SelfReferential
obj::SelfReferential
SelfReferential() = (x = new(); x.obj = x)
end
function deepcopy_internal(sr::SelfReferential, oidd::ObjectIdDict)
# if haskey(oidd,sr)
# return oidd[sr]
# else
new_obj = deepcopy_internal(sr,oidd)
new_sr = sr(new_obj)
oidd[sr] = new_sr
return new_sr
# end
end
sr = SelfReferential()
deepcopy_sr = deepcopy(sr)
Now this will break, since it runs in into an infinite recursion. Even if
you enable the lines which are commented out, it still breaks, but I don't
know why.
But as Yichao Yu has pointed out, the builtin deepcopy function works out
of the box for your custom type.
On Wednesday, August 24, 2016 at 9:02:19 AM UTC+2, Yichao Yu wrote:
>
>
>
> On Tue, Aug 23, 2016 at 5:19 PM, Tommy Hofmann <[email protected]
> <javascript:>> wrote:
>
>> Why do you think that deepcopy works on SelfReferential without defining
>> deepcopy_internal? Line 8 of deepcopy.jl is: deepcopy(x) =
>> deepcopy_internal(x, ObjectIdDict())
>>
>
> Because `deepcopy_internal` already handles this.
>
> You shouldn't need to define deepcopy_internal for custom types in
> general, unless your type needs special serialization support (e.g. if it
> has pointer to C memory)
>
>
>>
>>
>> On Tuesday, August 23, 2016 at 10:52:35 AM UTC+2, Chris Stook wrote:
>>>
>>> I created this simple example to try to understand deepcopy_internal.
>>>
>>> type SelfReferential
>>> obj::SelfReferential
>>>
>>> SelfReferential() = (x = new(); x.obj = x)
>>> end
>>>
>>> function deepcopy_internal(sr::SelfReferential, oidd::ObjectIdDict)
>>> # if haskey(oidd,sr)
>>> # return oidd[sr]
>>> # else
>>> new_obj = deepcopy_internal(sr,oidd)
>>> new_sr = sr(new_obj)
>>> oidd[sr] = new_sr
>>> return new_sr
>>> # end
>>> end
>>>
>>> sr = SelfReferential()
>>> deepcopy_sr = deepcopy(sr)
>>>
>>> This works, but deepcopy works on SelfReferential without defining
>>> deepcopy_internal, so this isn't a good
>>> example.
>>>
>>> How should this be modified so deepcopy_internal is required?
>>>
>>> Are the commented out lines of code necessary?
>>>
>>> Thanks,
>>> Chris
>>>
>>>
>
