Behaviour of append (~=)

[Daniel Keep]

Lionello Lunesu wrote:
> Why does the appending to a 'null' array cause the contents to be copied?
> 
> int[] ar1; // some array, not constant
> 
> int[] ar2 = null;
> ar2 ~= ar1;
> // ar2 !is ar1
> 
> But it could be like this:
> if (ar2)
>   ar2 ~= ar1;
> else
>   ar2 = ar1;
> 
> Wouldn't it be a good optimization for ~= to check for null first, to
> prevent the copy?
> 
> L.

I think the problem with this is that it's an edge case.  With your
suggestion, appending to a null array and appending to an *empty* array
would have completely different semantics.  Now, every programmer who
uses arrays has to watch out for this one special case.

Yes, it would be better performance-wise, but it would be hell on
programmers since it's non-obvious behaviour.

	-- Daniel

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