C++17 cannot beat D surely
Yuxuan Shui via Digitalmars-d
digitalmars-d at puremagic.com
Tue Jun 6 17:28:23 PDT 2017
On Sunday, 4 June 2017 at 04:39:21 UTC, Adam D. Ruppe wrote:
> On Sunday, 4 June 2017 at 04:34:44 UTC, Mike Parker wrote:
>> I would not have expected enum b = sort(a) to trigger an
>> allocation. auto b, yes, of course (and the disassembly from
>> that is not much different). So I'd love to see a blog post
>> explaining it.
>
> I don't think I can do a full-on blog post, but I can answer it
> in a couple sentences: `enum` is treated by the compiler just
> like literals. Array literals allocate at each usage point,
> therefore enum arrays allocate at each usage point. (*each*
> usage point)
I think the allocation is because sort returns a SortedRange, not
an array.
So even this allocates:
enum b = a.sort;
writeln(b[1]);
OTOH, this doesn't allocate:
enum b = a.sort.array;
writeln(b[1]);
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