Dynamic arrays in D 1.0

[Bill Baxter]

Janice Caron wrote:
> On 11/05/2008, Bill Baxter <dnewsgroup at billbaxter.com> wrote:
>> Janice Caron wrote:
> 
>>> To erase the elements from index i to index j in place:
>>  It can be done more efficiently using memmove to shift contents down. Also
>> if you're dropping the tail end, you can just change .length. Cashew's erase
>> routine (called "dropRange") does both.
> 
> OK, how about this, using std.algorithm.copy:
> 
>     array = copy(array[j..$], array[i..$]);
>     array = array[0..$+i-j];
> 
> The copy is done in-place, like memmove(), but without the danger of
> buffer overrun.

Std.algorithm's copy(), in its current form, will be less efficient 
because it copies elements one-at-a-time in a loop.  This was what the 
first version of Cashew did, but it was benchmarked and found that 
memmove is faster.

Of course, std.algorithm.copy could probably be tweaked to use memmove 
when possible, and then that would be just as good.  But right now it 
isn't.

Anyway, the existence of such subtleties is why things like erase should 
just be in the darn standard library so the problem only has to be 
solved once.

> You still need the second line to change the length though.
> 
> You can even do it ONE LINE, but I have to confess, the code looks
> pretty obfuscated.
> 
>     array = array[0..$-copy(array[j..$], array[i..$]).length];

Yeh, don't do that.  :-)

--bb