Zero length arrays in D

[H. S. Teoh]

On Mon, Feb 18, 2019 at 01:34:37PM +0000, Eduard Staniloiu via Digitalmars-d-learn wrote:
> Hello
> 
> According to the spec[0], D supports zero length arrays [1].

Huh. I didn't even know D was supposed to support this.  I found a few
examples of this usage in Adam Ruppe's arsd code, where the zero-length
array is sliced as you indicated:

	struct X {
		int[0] data;
	}
	X* x = ...;

	int[] arr = x.data.ptr[0 .. n];
	arr[i] = ...;


[...]
> Attempting to use the zero-length array results in a compiler error
> 
> `a.contents[2]` -> Error: array index 2 is out of bounds
> (*a).contents[0 ..  0]

Yeah this needs to be explicated in the docs / spec.


> The way I've used around this error is "safely" break/trick the type
> system
> 
> ```
>     int *p = a.contents.ptr;
>     int[] p_cont = p[0 .. n];
>     p_cont[2] = 10; // fine
> ```
> 
> Is this the intended way of working with zero length arrays?
[...]

No idea.  But it's probably the only way of actually using them right
now. :-D  The spec / docs need to be updated.


T

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