Ranges

[pascal111]

On Thursday, 4 August 2022 at 22:14:26 UTC, Ali Çehreli wrote:
> On 8/4/22 11:05, frame wrote:
>
> > `popFront()`
>
> The function was this:
>
>        void popFront() {
>           students = students[1 .. $];
>        }
>
> > copies all
> > elements except the first one into the variable (and
> overwrites it), so
> > it moves the data forward.
>
> That would be very slow. :) What actually happens is, just the 
> two variables that define a slice is adjusted.
>
> Slices consist of two members:
>
> struct __an_int_D_array_behind_the_scenes {
>   size_t length;
>   int * ptr;
> }
>
> So,
>
>   students = students[1..$];
>
> is the same as doing the following:
>
>   students.length = (students.length - 1);
>   students.ptr = students.ptr + 1;
>
> (ptr's value would change by 4 bytes because 'int'.)
>
> No element is copied or moved. :)
>
> Ali

I didn't notice that all what we needs to pop a range forward is 
just a slice, yes, we don't need variable here.