std.algorithm.remove strange behavior (removing items for the dynamic array)

[Jonathan M Davis]

On Friday, May 11, 2012 08:15:45 Jacob Carlborg wrote:
> On 2012-05-11 05:18, Jonathan M Davis wrote:
> >> ...and got the following output:
> >> 
> >> 
> >> a before: [2, 4, 8, 16, 32, 64, 128]
> >> a after : [2, 4, 8, 32, 64, 128, 128]
> >> a after2: [2, 8, 32, 64, 128, 128, 128]
> >> 
> >> 
> >> I'm confused.
> >> Please tell me is it normal behavior of this function or is it a
> >> bug?
> >> Maybe i'm doing something wrong?
> >> Maybe i need another "remove" or maybe it's normal to use slicing
> >> to remove array's items (like a = a[0..i] ~ [i+1..$]) ?
> >> 
> >> Thanx for attention.
> >> 
> >> P.S. I'm sorry if my english confuses you.
> > 
> > No. As the documentation for remove explains, this is completely expected.
> > remove removes elements from _the range_, not the container. It can't
> > remove elements from the container (regardless of the container or range
> > type), because it doesn't understand anything about the container. It
> > shifts the elements forward in the range and returns a range which is
> > reduced in length by the number of elements removed, but the original
> > range is not reduced in size, nor is the underlying container reduced in
> > size (all of which is slightly more confusing with dynamic arrays,
> > because the range _is_ the container, which is not the case in general).
> > Also, some ranges don't even _have_ an underlying container, so remove
> > _definitely_ can't remove anything from the container itself - only shift
> > elements. C++'s erase function has the exact same problem.
> 
> Is it supposed to change the underlying array like that? It doesn't
> print the original sequence.

Yes. To remove an element, it shifts all of the elements to the right of that 
element over by one. It just doesn't change the elements on the end when it 
shifts elements over, so the last element gets duplicated.

- Jonathan M Davis