fast way to insert element at index 0

[Baz via Digitalmars-d-learn]

On Tuesday, 23 June 2015 at 11:22:31 UTC, Steven Schveighoffer 
wrote:
> On 6/23/15 1:51 AM, jkpl wrote:
>> On Tuesday, 23 June 2015 at 05:16:23 UTC, Assembly wrote:
>>> [...]
>>
>> * Option 1/
>>
>> if most of the time you have to insert at the beginning, then 
>> start
>> reading from the end and append to the end, so that the 
>> existing block
>> has not to be moved. You just have to add val at the end.
>>
>> * Option 2/
>>
>> better way to move the whole block (this can be done with 
>> memmove too).
>>
>> ---
>> void push(T val)
>> {
>>      buffer.length += 1;
>>      buffer[1..$] = buffer[0..$-1];
>
> This will fail.
>
> http://dlang.org/arrays.html#overlapping-copying
>
> I will note, dcollections had a deque, which allowed insertion 
> at the front in O(1) (amortized) time. It basically worked by 
> having 2 arrays front to front.
>
> -Steve

according to the C library, memmove handle overlapps, you 
mismatch with memcpy which does not.