Bug or feature? This one caught me by surprise:

void main() {
    {
        int[string] aa[string];
        aa["foo"]["bar"] = 1;
        assert(aa["foo"]["bar"] == 1); //ok

        auto aa2 = aa;
        aa2["boo"]["dar"] = 2;
        assert(aa["foo"]["bar"] == 1); //ok
    }

    {
        int[string] aa[string]; //not set to anything yet

        auto aa2 = aa;
        aa2["boo"]["dar"] = 2;
        assert(aa["foo"]["bar"] == 1); //oops
    }
}

It seems that assigning an AA to another makes both point at the same data only if the first array has data to begin with. Is that the expected behaviour?

Atila

On Monday, 2 December 2013 at 13:30:44 UTC, Atila Neves wrote:
> Bug or feature? This one caught me by surprise:
>
> void main() {
>     {
>         int[string] aa[string];
>         aa["foo"]["bar"] = 1;
>         assert(aa["foo"]["bar"] == 1); //ok
>
>         auto aa2 = aa;
>         aa2["boo"]["dar"] = 2;
>         assert(aa["foo"]["bar"] == 1); //ok
>     }
>
>     {
>         int[string] aa[string]; //not set to anything yet
>
>         auto aa2 = aa;
>         aa2["boo"]["dar"] = 2;
>         assert(aa["foo"]["bar"] == 1); //oops
>     }
> }
>
> It seems that assigning an AA to another makes both point at the same data only if the first array has data to begin with. Is that the expected behaviour?
>
> Atila

I would say it is consequence of current implementation, and, taking into account ongoing efforts to rewrite AA implementation, this special detail of null AA behavior may one day be gone.

Atila Neves:

>         int[string] aa[string];

Don't mix C style array definitions with D style ones :-) Always use the D-style, unless you are porting C code (and refactor it later).

Bye,
bearophile

On Monday, 2 December 2013 at 15:13:48 UTC, bearophile wrote:
> Atila Neves:
>
>>        int[string] aa[string];
>
> Don't mix C style array definitions with D style ones :-) Always use the D-style, unless you are porting C code (and refactor it later).

How would that go in this case?

Atila Neves:

> How would that go in this case?

An example usage:

void main() {
    int[float][string] aa;
    aa["foo"][1.5] = 1;
}

Bye,
bearophile

On Monday, 2 December 2013 at 13:30:44 UTC, Atila Neves wrote:
> It seems that assigning an AA to another makes both point at the same data only if the first array has data to begin with. Is that the expected behaviour?
>
> Atila

You've been hit by the null associative array not being the same as an empty associative array. See discussion:

http://forum.dlang.org/post/wovnuggqtscsbgnjcpua@forum.dlang.org

On Tuesday, 3 December 2013 at 03:14:46 UTC, Jesse Phillips wrote:
> On Monday, 2 December 2013 at 13:30:44 UTC, Atila Neves wrote:
>> It seems that assigning an AA to another makes both point at the same data only if the first array has data to begin with. Is that the expected behaviour?
>>
>> Atila
>
> You've been hit by the null associative array not being the same as an empty associative array. See discussion:
>
> http://forum.dlang.org/post/wovnuggqtscsbgnjcpua@forum.dlang.org

Sigh. If at least there was a way to declare them empty...

On Monday, 2 December 2013 at 16:52:51 UTC, bearophile wrote:
> Atila Neves:
>
>> How would that go in this case?
>
> An example usage:
>
> void main() {
>     int[float][string] aa;
>     aa["foo"][1.5] = 1;
> }
>
> Bye,
> bearophile

Oh. That makes sense. Doh!

I guess I was focussing on "key to AA of..." and that's why I wrote it that way.