void[] vs ubyte[] - differences?

[Nick Treleaven]

On Wednesday, 16 July 2025 at 13:29:01 UTC, z wrote:
> I also see this in the language documentation :
> ```
> A void array cannot be indexed.
> ```
> But i can slice it just fine in DMD 2.111...
>
> Is this by design or is there a hole in the language 
> specification?

The sentence before says:

> Array indices in slicing operations are interpreted as byte 
> indices

And the example shows slicing:
```d
     void[] arr = data1;            // OK, int[] implicit converts 
to void[].
...
     arr[0..4] = [5];               // Assign first 4 bytes to 1 
int element
```

Slicing a void array is useful as it can refer to multiple bytes. 
Indexing a void array is not really useful because if the array 
is only holding bytes, then why not use byte[] instead? If it's 
not a byte, then indexing it is probably wrong anyway (either by 
design, or because dealing with a single byte at a time is 
inefficient).

> By extension what the differences between `void`, `ubyte`, 
> `void[]`, `ubyte[]` really? The language documentation doesn't 
> appear to be explaining everything.
> Thanks in advance

The docs explain the difference between the two array types. 
Perhaps there should be an entry for `void` in the types page. A 
`void` value cannot be accessed. `void.sizeof` is 1 so that a 
void array can have length equivalent to the number of bytes in 
the array.