Properties: a.b.c = 3

[Steven Schveighoffer]

On Wed, 29 Jul 2009 10:16:33 -0400, grauzone <none at example.net> wrote:

> Daniel Keep wrote:
>> Maybe the compiler could rewrite the above as:
>>  auto t = a.b;
>> t.c = 3;
>> a.b = t;
>>  Unless it can prove it doesn't need to.  Same solution as to the op=
>> conundrum.
>
> Yes! At least that's what the user wants.
>
> The compiler has to detect, that the object was modified at all. (To  
> know whether it should generate code to write back the property.) Would  
> this make the compiler much complexer?
>
> You also have to deal with nested properties:
>
> a.b.c.d = 3;
>
> turns to
>
> auto t = a.b;
> auto t2 = t.c;
> c.d = 3;
> t.c = t2;
> a.b = t;
>
> ???

Yeah, I think this idea is no good.  a.b.c.d.e.f = 3, results in one  
gigantic mess, which the user might not want.

Properties don't have to be exactly like fields.  I think we need to get  
away from that idea.

It would be nice if the compiler could help by simply rejecting what it  
can reject (assignment to rvalues), but other than that, there's not much  
that can be done.

This can be detected in simple cases, but in the case where the end point  
is a function, it will be difficult or impossible.

I don't believe the problem needs to be solved.

-Steve