Re: How do you remove/insert elements in a dynamic array without allocating?

[bearophile]

Malte Skarupke:

void main()
{
    import core.memory;
    GC.disable();
    scope(exit) GC.enable();

    int[] a = [1, 2, 3, 4, 5];
    foreach(i; 0 .. 1000000000)
    {
        --a.length;
        a ~= i;
    }
}

That loop will keep on allocating in every iteration until your memory is full.

Is there a way to do something similar to this without allocating?

void main() {
    auto array = [1, 2, 3, 4, 5];
    array.assumeSafeAppend();
    foreach (i; 0 .. 10_000_000) {
        array.length--;
        array ~= i;
    }
}

But neither one works.

And that's good, it was designed that way on purpose :-)

How do you work with the dynamic array without having to rely on the GC all the time?

There are various ways to do it...

I want something similar to the stl vector, which only re-allocates once your array grows past a certain size, not on every append.

D arrays already work like this.

Bye,
bearophile