Arrays are sufficient for ArrayLists? Really??

[Mehrdad]

On 5/16/2011 12:25 PM, Andrei Alexandrescu wrote:
> On 5/16/11 2:25 PM, Timon Gehr wrote:
>> Mehrdad wrote:
>>> Timon:
>>>> What about:
>>> void removeAt(T)(ref T[] arr, size_t index)
>>> {
>>> foreach (i, ref item; arr[1 .. index+1])
>>> item = arr[i - 1];
>>> arr = arr[1 .. $]; //note how no valid data is beyond the end of the
>>> array
>>> }
>>>
>>> Clever, but if you do this with a big enough number of items, you'll
>>> exhaust all memory. Be careful. :P
>>
>> Total memory usage is at most 2 times the maximum size the array
>> reaches during
>> its lifetime. Test it.
>
> Testing would also reveal that this is a buggy replica of
> std.algorithm.remove. At best we should suggest reusing library code
> over attempting to reinvent it.
>
>
> Thanks,
>
> Andrei
>

Oh, I see.
Wait, what bug are you referring to, though?


On 5/16/2011 12:25 PM, Steven Schveighoffer wrote:
 >> Steven:
 >>> For the OP, you may want to consider using ArrayList from
 >> dcollections, which supports removing an individual or range of
 >> elements, or using foreach to purge the list. Note that this class
 >> does call assumeSafeAppend on its data storage since it can make
 >> more assumptions.
 >>
 >> Ah, seems to be what I need.
 >>
 >> I guess I was also trying to argue this should really be part of the
 >> language too, though (not just Phobos), given that concatenation and
 >> even hashtables are also part of the language. It seems to be
 >> missing badly. :\
 >
 > builtin arrays are full of features that are "good enough" for most
 > usages. Removing elements the way that is least confusing is
 > inefficient, and removing elements the most efficient way can be
 > confusing or incorrect depending on the application. Rather than guess
 > what the user expects, the runtime just leaves it up to the
 > developer/standard lib.
 >
 > -Steve

Hm... is it really that atypical, though? We already have addition, is 
removal really that unlikely of an operation?