On 19/02/2012 15:05, Daniel Murphy wrote:
> "Ben Davis"<entheh@cantab.net>  wrote in message
> news:jhr0qf$24sj$1@digitalmars.com...
>> On 19/02/2012 03:31, Daniel Murphy wrote:
>>> Except for this magic initialization, AAs behave the same as classes - ie
>>> a
>>> reference type.
>>
>> That's not quite true, because 'length' is passed around by value
>> alongside the reference, leading to semantics you could never reproduce
>> with classes, unless I'm mistaken.
>
> AAs, not Arrays.

Ah, well then I did this test earlier:

int[string] assoc=null;
writefln("%s",assoc.length);
//prints 0

Why did that work?

The call is rewriten to _aa_len(aa) and checks for null.

This can almost be done with a normal class, except the compiler inserts a null check into each member function, iirc.

I guess that's another bit of magic that can't be handled simply.

It can still be done with a struct:

struct AAPimpl
{
   AAImpl aa;
   size_t length() @property
   {
      if (!aa) return 0;
      return aa.length();
   }
}

I expect something like this will end up being the solution.

"Ben Davis" <entheh@cantab.net> wrote in message news:jhr4d1$2b4n$1@digitalmars.com...
> On 19/02/2012 15:05, Daniel Murphy wrote:
>> "Ben Davis"<entheh@cantab.net>  wrote in message news:jhr0qf$24sj$1@digitalmars.com...
>>> On 19/02/2012 03:31, Daniel Murphy wrote:
>>>> Except for this magic initialization, AAs behave the same as classes -
>>>> ie
>>>> a
>>>> reference type.
>>>
>>> That's not quite true, because 'length' is passed around by value alongside the reference, leading to semantics you could never reproduce with classes, unless I'm mistaken.
>>
>> AAs, not Arrays.
>
> Ah, well then I did this test earlier:
>
> int[string] assoc=null;
> writefln("%s",assoc.length);
> //prints 0
>
> Why did that work?