Error: xxx is not an lvalue

[Unknown W. Brackets]

If that's the structure, then yes, I agree.

Long time ago (before D 1.x?) I looked at the associative array 
implementation and it was a struct with a few members.  I didn't realize 
it had changed.  Or maybe I'm just remembering wrong.

-[Unknown]


Steven Schveighoffer wrote:
> On Mon, 04 May 2009 14:53:41 -0400, Unknown W. Brackets 
> <unknown at simplemachines.org> wrote:
> 
>> I've always though of arrays and associative arrays as structs (which 
>> really is what they are.)  Thinking that way, this behavior makes 
>> exact sense - down to .length being unchangeable and associative 
>> arrays being unchangeable.
>>
>> I mean, you wouldn't want to make it work the way you suggest by 
>> making arrays and associative arrays simply pointers to their current 
>> structs (just like a class would be.)  You could make such a class 
>> easily yourself, anyway.
>>
>> If you are right, I guess the right solution would be to make the ref 
>> implicit when returning (or, I suppose, passing?) such arrays and 
>> associative arrays.  But that seems wrong to me too, and wouldn't come 
>> free (speaking of efficiency) either.
>>
>> -[Unknown]
>>
> 
> The underlying struct of an AA is:
> 
> struct AA
> {
>    AA_Implementation *impl;
> }
> 
> or something like that ;)  Look at the D runtime source.
> 
> But in any case, if you return an array slice, would you not want to be 
> able to update an element of the slice?
> 
> I think there is a difference between a value struct (where all 
> internals are non-reference types), and a reference struct (where at 
> least one element is a reference type).  A reference struct should be 
> able to pass those references to other functions without having to be 
> ref'd.  It forces non-transparent type wrapping if that isn't the case.  
> I should be able to replace a reference or pointer type with a wrapper 
> struct where I can modify the interface, and it should be transparent 
> that I have done so (except for the interface changes of course).  I 
> think this is one of the goals D2 is working towards.
> 
> It makes sense that a value struct or the value types inside a reference 
> struct (i.e. the length of an array) should not be changeable as 
> rvalues, since you aren't going to use them later.
> 
> Both arrays (as the current implementation) and AA's are reference structs.
> 
> -Steve