Lets say I've got 3 overloads of opIndexAssign:

auto opIndexAssign(T t);
auto opIndexAssign(T t, size_t i); and
auto opIndexAssign(T t, size_t[2] i);

I would assume to return what I would return with opIndex but I'd rather not act upon assumptions.
But if yes is it supposed to be the newly assigned values or the pre-assignment ones ? By value or by reference ? And if it's the new stuff can I just return t ?

The language manual on operator overloading didn't answer that question and neither did an internet search which didn't find any useful information. Something unrelated and a heads up about introducing opIndexAssign from 2004.

On Tuesday, 25 February 2020 at 11:02:40 UTC, wjoe wrote:
> Lets say I've got 3 overloads of opIndexAssign:
>
> auto opIndexAssign(T t);
> auto opIndexAssign(T t, size_t i); and
> auto opIndexAssign(T t, size_t[2] i);
>
> I would assume to return what I would return with opIndex but I'd rather not act upon assumptions.
> But if yes is it supposed to be the newly assigned values or the pre-assignment ones ? By value or by reference ? And if it's the new stuff can I just return t ?
>
> The language manual on operator overloading didn't answer that question and neither did an internet search which didn't find any useful information. Something unrelated and a heads up about introducing opIndexAssign from 2004.

opIndexAssign is the operator used in the following code:

arr[1] = 8;

It returns the element at index 1 (so 8 in this case) by reference.
This allows you to do:

(arr[1] = 8)++;
assert(arr[1] == 9);

Whether or not you want to support this behavior in your custom data structure is up to you. It's perfectly valid to return the element by value or even return void.

Returning void from any custom assignment operator is always a safe choice. It's possible that some algorithms (e.g. in Phobos or third-party libraries) may need op*Assign to return something, but in that unlikely case you'll get a compile-time error, so it will be an easy fix.

On Tuesday, 25 February 2020 at 11:49:50 UTC, Petar Kirov [ZombineDev] wrote:
> On Tuesday, 25 February 2020 at 11:02:40 UTC, wjoe wrote:
>> [...]
>
> opIndexAssign is the operator used in the following code:
>
> arr[1] = 8;
>
> It returns the element at index 1 (so 8 in this case) by reference.
> This allows you to do:
>
> (arr[1] = 8)++;
> assert(arr[1] == 9);
>
> Whether or not you want to support this behavior in your custom data structure is up to you. It's perfectly valid to return the element by value or even return void.
>
> Returning void from any custom assignment operator is always a safe choice. It's possible that some algorithms (e.g. in Phobos or third-party libraries) may need op*Assign to return something, but in that unlikely case you'll get a compile-time error, so it will be an easy fix.

Excellent answer ! Thanks for your fast reply :)

On 2/25/20 3:02 AM, wjoe wrote:> Lets say I've got 3 overloads of opIndexAssign:
>
> auto opIndexAssign(T t);

> an internet search which didn't find any useful
> information.

I have examples for non-templatized and templatized versions of opIndexAssign here:


http://ddili.org/ders/d.en/operator_overloading.html#ix_operator_overloading.opIndexAssign


http://ddili.org/ders/d.en/templates_more.html#ix_templates_more.opIndexAssign%20template

I used this index to find those:

  http://ddili.org/ders/d.en/ix.html

Ali

On Tuesday, 25 February 2020 at 15:30:19 UTC, Ali Çehreli wrote:
> On 2/25/20 3:02 AM, wjoe wrote:> Lets say I've got 3 overloads of opIndexAssign:
> >
> > auto opIndexAssign(T t);
>
> > an internet search which didn't find any useful
> > information.
>
> I have examples for non-templatized and templatized versions of opIndexAssign here:
>
>
> http://ddili.org/ders/d.en/operator_overloading.html#ix_operator_overloading.opIndexAssign
>
>
> http://ddili.org/ders/d.en/templates_more.html#ix_templates_more.opIndexAssign%20template
>
> I used this index to find those:
>
>   http://ddili.org/ders/d.en/ix.html
>
> Ali

This is great! Thank you. Curious why this wasn't found by my internet search.