这样做，而

void main()
{
    import std.stdio : writeln;
    int[] arr = [1, 3, 4];
    int i = 0;
    assert(arr.length > 0, "Array must contain at least one element");
    do
    {
        arr[i++] *= 2;
    } while (i < arr.length);
    writeln(arr); // [2, 6, 8]
}