Properties: a.b.c = 3

[grauzone]

Steven Schveighoffer wrote:
> 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.

I don't want to type out that mess as a user either...

Design changes to avoid that mentioned mess would interfere with the 
goal of abstraction (e.g. assume you have widget.position, now how do 
you set only the x coordinate? yeah, split the property into position_x 
and position_y. Result is you have more noise, and you can't use a Point 
struct.)

As for the rest, I'm sure all of you will have figured it out after some 
more ~500 postings.