Difference between slice[] and slice

[ag0aep6g]

On 25.09.19 22:36, WhatMeWorry wrote:
> On Wednesday, 25 September 2019 at 19:25:06 UTC, Ali Çehreli wrote:
>> On 09/25/2019 12:06 PM, WhatMeWorry wrote:
[...]
>> > In short, is there anytime that one would want to use
>> "slice[] =
>> > something" syntax?I
>>
>> That changes element values.
> 
> Ok.  But which element(s)?

All of them. For example, `slice[] = 42;` sets all elements to 42. And 
`slice[] = another_slice[];` replaces all elements of `slice` with 
copies of `another_slice`'s elements.

>  In my specific case, I was using []. Is
> 
> waste[] = waste[0..$-1];
> 
> even semantically meaningful?  Because the LDC compiler had no problem 
> compiling it.

It's equivalent to this:

----
waste[0] = waste[0..$-1][0];
waste[1] = waste[0..$-1][1];
...
waste[waste.length - 2] = waste[0..$-1][waste.length - 2];
waste[waste.length - 1] = waste[0..$-1][waste.length - 1];
----

So it basically does nothing. It just copies `waste`'s elements over 
themselves.

Except that the last line makes an out-of-bounds access. That's an error 
that may be detected during compilation or at run time. Or if you're 
telling the compiler to optimize too aggressively, it might go unnoticed.