Array Design Idea

[Craig Black]

"Jb" <jb at nowhere.com> wrote in message news:fjk5g9$10lb$1 at digitalmars.com...
>
> "Craig Black" <cblack at ara.com> wrote in message 
> news:fjk2k6$pfl$1 at digitalmars.com...
>
>> There are three things that need to be stored for a resizable array:  the 
>> pointer to the array, the size, and the capacity.  My array 
>> implementation, both the size and the capacity are stored on the heap 
>> with the array.  There is only one heap allocation, and the first 8 bytes 
>> are reserved for the size and capacity values.  Further, there is no heap 
>> allocation if the array is empty.  If the array is empty, then the 
>> pointer is null, and the array is assumed to have a size and capacity of 
>> zero, so there is no need to store the size or capacity of an empty 
>> array.
>
> Thats how Delphi does dynamic arrays and strings. Well except that it has 
> length & refcount rather than length & capacity. Wouldnt it break slicing 
> though? You cant point halfway into an existing array and still have the 
> length & capacity at -4,-8 bytes?

I still haven't wrapped my head around the slicing issue.  Obviously it's 
not an issue for C++ arrays.  Doesn't D already allocate the capacity of the 
array on the heap?  If this is so why doesn't this break slicing?