Hello again.

I'm designing a template version of a BST.

Because of this, I want to be able to compare if two objects of the same class type are references to the same anonymous class on the heap somewhere.

Example:

On Saturday, 3 June 2017 at 19:57:47 UTC, Mark wrote:
> Hello again.
>
> I'm designing a template version of a BST.
>
> Because of this, I want to be able to compare if two objects of the same class type are references to the same anonymous class on the heap somewhere.
>
> Example:

Not sure what happened there.

Anyways, example:

auto A = new Box();
auto B = new Box();

if(A.opEquals(B)) {}

gives the error
test.o:(.data.rel.ro+0x18): undefined reference to `_D5Stack12__ModuleInfoZ'
collect2: error: ld returned 1 exit status
Error: linker exited with status 1

if(Object.opEquals(A,B) gives

test.d(10): Error: function object.Object.opEquals (Object o) is not callable using argument types (Box, Box)


How do I got about comparing two objects then??
Thanks.

On Saturday, 3 June 2017 at 20:02:13 UTC, Mark wrote:
> On Saturday, 3 June 2017 at 19:57:47 UTC, Mark wrote:
>> Hello again.
>>
>> I'm designing a template version of a BST.
>>
>> Because of this, I want to be able to compare if two objects of the same class type are references to the same anonymous class on the heap somewhere.
>>
>> Example:
>
> Not sure what happened there.
>
> Anyways, example:
>
> auto A = new Box();
> auto B = new Box();
>
> if(A.opEquals(B)) {}
>
> gives the error
> test.o:(.data.rel.ro+0x18): undefined reference to `_D5Stack12__ModuleInfoZ'
> collect2: error: ld returned 1 exit status
> Error: linker exited with status 1
>
> if(Object.opEquals(A,B) gives
>
> test.d(10): Error: function object.Object.opEquals (Object o) is not callable using argument types (Box, Box)
>
>
> How do I got about comparing two objects then??
> Thanks.

I think that the error is unrelated. Which dmd do you use ?

Otherwise, opEquals (or just == ) is well the way to follow. By default Object.opEquals just compare the Objects addresses. If you want to perform a deep comparison (i.e the members) you have to override opEquals.

On Saturday, 3 June 2017 at 20:02:13 UTC, Mark wrote:
> On Saturday, 3 June 2017 at 19:57:47 UTC, Mark wrote:
>> Hello again.
>>
>> I'm designing a template version of a BST.
>>
>> Because of this, I want to be able to compare if two objects of the same class type are references to the same anonymous class on the heap somewhere.
>>
>> Example:
>
> Not sure what happened there.
>
> Anyways, example:
>
> auto A = new Box();
> auto B = new Box();
>
> if(A.opEquals(B)) {}
>
> gives the error
> test.o:(.data.rel.ro+0x18): undefined reference to `_D5Stack12__ModuleInfoZ'
> collect2: error: ld returned 1 exit status
> Error: linker exited with status 1
>
> if(Object.opEquals(A,B) gives
>
> test.d(10): Error: function object.Object.opEquals (Object o) is not callable using argument types (Box, Box)
>
>
> How do I got about comparing two objects then??
> Thanks.

Could you please systematically post compilable code? It is very hard to say anything without even seeing what you're struggling with.

On 06/03/2017 10:02 PM, Mark wrote:

> auto A = new Box();
> auto B = new Box();
> 
> if(A.opEquals(B)) {}
> 
> gives the error
> test.o:(.data.rel.ro+0x18): undefined reference to `_D5Stack12__ModuleInfoZ'
> collect2: error: ld returned 1 exit status
> Error: linker exited with status 1

Your code works for me (when adding `class Box {}` and a `main` function). An "undefined reference" error can mean that you forgot to include a module on the command line.

> if(Object.opEquals(A,B) gives
> 
> test.d(10): Error: function object.Object.opEquals (Object o) is not callable using argument types (Box, Box)

Yeah, that's not how you do it.

> How do I got about comparing two objects then??
> Thanks.

Just use the usual equality operator: `==`. Or if you want to check for identity, use the binary `is` operator.

----
class Box {}

void main()
{
    auto A = new Box();
    auto B = new Box();

    if (A == B) {}
    if (A is B) {}
}
----

By default, they act the same. But you can change how `==` behaves by overriding `opEquals`. You cannot override `is`.

On Saturday, 3 June 2017 at 20:24:44 UTC, ag0aep6g wrote:

> By default, they act the same. But you can change how `==` behaves by overriding `opEquals`. You cannot override `is`.



Ok. So by using '==' it should compare the addresses of the objects?

I think I didn't include the other file as an argument on the command line (Oops!)

I'm using dmd v2.074.0.

In the future I'll include a compilable example. I was having problems with a class I made which is about 45 lines, that might be a lot of code for a post.

But it seems to work now. This is good, I can have the comparisons work for any type without doing backflips.


Thanks.

On Saturday, 3 June 2017 at 22:38:31 UTC, Mark wrote:
...
> Thanks.

Actually, I got another question,

how Can I obtain the actual memory address of a class?

I'll still need to solve the problem of taking ints/floats/reals etc., as well as structs and classes and sending them right/left in the BST. :/


Thanks again.

On Saturday, 3 June 2017 at 22:38:31 UTC, Mark wrote:

> In the future I'll include a compilable example. I was having problems with a class I made which is about 45 lines, that might be a lot of code for a post.

You can use external resources such as:

https://d.godbolt.org/
https://dpaste.dzfl.pl

to paste code there and then just post a link to a paste here.

On Saturday, 3 June 2017 at 22:52:42 UTC, Mark wrote:

> Thanks again.

Nevermind, I got it.

On Saturday, 3 June 2017 at 22:53:51 UTC, Stanislav Blinov wrote:
> On Saturday, 3 June 2017 at 22:38:31 UTC, Mark wrote:
>
>> In the future I'll include a compilable example. I was having problems with a class I made which is about 45 lines, that might be a lot of code for a post.
>
> You can use external resources such as:
>
> https://d.godbolt.org/
> https://dpaste.dzfl.pl
>
> to paste code there and then just post a link to a paste here.

I'll keep that in mind, thanks.