• Tim (12/12) Sep 28 2021 I'm doing the following:
• Adam Ruppe (12/18) Sep 28 2021 Here the window[] takes a variable-length slice of it. Turning it
• Tim (2/18) Sep 28 2021 Perfect answer. Thanks for clearing that all up mate

Tim <tim.oliver tutanota.com> writes:

I'm doing the following:

```D
int[25] window = 0;

// Later in a loop
window = someInteger ~ window[].dropBackOne;
```

But I'm struggling to understand why the following doesn't work
```D
window = someInteger ~ window.dropBackOne;
```

What does the `[]` do exactly? Is an array not a bidirectional 
range?

Adam Ruppe <destructionator gmail.com> writes:

On Tuesday, 28 September 2021 at 22:56:17 UTC, Tim wrote:
 I'm doing the following:

 int[25] window = 0;

Note that this array has a fixed size.

 window = someInteger ~ window[].dropBackOne;

Here the window[] takes a variable-length slice of it. Turning it 
from int[25] into plain int[]. Then you can drop one since it is 
variable length. Then appending again ok cuz it is variable. Then 
the window assign just copies it out of the newly allocated 
variable back into the static length array.

 window = someInteger ~ window.dropBackOne;

But over here you are trying to use the static array directly 
which again has fixed length, so it is impossible to cut an item 
off it or add another to it.

 What does the `[]` do exactly? Is an array not a bidirectional 
 range?

It takes a slice of the static array - fetching the pointer and 
length into runtime variables.

Tim <tim.oliver tutanota.com> writes:

On Tuesday, 28 September 2021 at 23:12:14 UTC, Adam Ruppe wrote:
 On Tuesday, 28 September 2021 at 22:56:17 UTC, Tim wrote:
 [...]

 Note that this array has a fixed size.

 [...]

 Here the window[] takes a variable-length slice of it. Turning 
 it from int[25] into plain int[]. Then you can drop one since 
 it is variable length. Then appending again ok cuz it is 
 variable. Then the window assign just copies it out of the 
 newly allocated variable back into the static length array.

 [...]

 But over here you are trying to use the static array directly 
 which again has fixed length, so it is impossible to cut an 
 item off it or add another to it.

 [...]

 It takes a slice of the static array - fetching the pointer and 
 length into runtime variables.

Perfect answer. Thanks for clearing that all up mate