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Casting an array form an associative array
Nov 10, 2012
Jacob Carlborg
Nov 10, 2012
Timon Gehr
Nov 10, 2012
Jacob Carlborg
```The following example:

void main()
{
void[][size_t] aa;
aa[1] = [1, 2, 3];

if (auto a = 1 in aa)
{
writeln(*(cast(int[]*) a));
writeln(cast(int[]) *a);
}
}

Will print:

[1, 2, 3, 201359280, 0, 0, 0, 0, 0, 0, 0, 0]
[1, 2, 3]

The first value seems to contain some kind of garbage. Why don't these two cases result in the same value?

--
/Jacob Carlborg
```
```On 11/10/2012 01:20 PM, Jacob Carlborg wrote:
> The following example:
>
> void main()
> {
>      void[][size_t] aa;
>      aa[1] = [1, 2, 3];
>
>      if (auto a = 1 in aa)
>      {
>          writeln(*(cast(int[]*) a));
>          writeln(cast(int[]) *a);
>      }
> }
>
> Will print:
>
> [1, 2, 3, 201359280, 0, 0, 0, 0, 0, 0, 0, 0]
> [1, 2, 3]
>
> The first value seems to contain some kind of garbage. Why don't these
> two cases result in the same value?
>

The length of an array is the number of elements. sizeof(void)==1 and sizeof(int)==4. The first example reinterprets the ptr and length pair of the void[] as a ptr and length pair of an int[]. The second example adjusts the length so that the resulting array corresponds to the same memory region.
```
```On 2012-11-10 17:48, Timon Gehr wrote:

> The length of an array is the number of elements. sizeof(void)==1 and
> sizeof(int)==4. The first example reinterprets the ptr and length pair
> of the void[] as a ptr and length pair of an int[]. The second example
> adjusts the length so that the resulting array corresponds to the same
> memory region.

Ok, thanks for the explanation.

--
/Jacob Carlborg
```