Re: Setting array length to 0 discards reserved allocation?

[Andrew Godfrey via Digitalmars-d]

On Sunday, 17 August 2014 at 07:33:01 UTC, ketmar via 
Digitalmars-d wrote:
On Thu, 14 Aug 2014 06:46:40 +0000
Andrew Godfrey via Digitalmars-d <digitalmars-d@puremagic.com> 
wrote:

sorry for the late answer.

Don't think I'm being flippant, but I have trouble 
interpreting such feedback, because D's dynamic array 
semantics ARE complicated.
and it will be even more complicated if we will rename 'em to 
'array
references'.

i completely agree that D dynarray docs can be made clearer and 
i
appreciate any efforts which makes docs better. i'm just against
'reference' term -- seems that i'm from that minority that 
becomes
immediately confused when reading 'array reference'. what i 
expect from
'reference' is that this code works:

  void foo (int[] a) {
    a ~= 42;
  }
  ...
  int[] arr;
  arr ~= 666;
  foo(arr);
  assert(arr.length == 2 && arr[1] == 42);

but it doesn't. so arrays clearly aren't 'references' (as 
'reference',
to my opinion, should keep 'pass by reference' semantics in 
this case).

so maybe we should coin some new word to describe dynarrays in 
D.

Maybe. But consider that if "a" was a class and "~=" was instead
"=", you would have the same confusion. As in:
 void foo(MyClass a) {
    a = new MyClass;
 }

In either case, we are "passing a reference by value".
So operations on the referent affect the passed object/array, but 
operations
on the reference do not.

The further surprise is caused because concatenation affects the 
_reference_.
In fact it doesn't affect the referent at all!
Good example. Consider that this works:

void foo (int[] a) {
  a[0] = 42;
}

int[] arr;
arr ~= 666;
foo(arr);
assert(arr.length == 1 && arr[0] == 42);