Properties: a.b.c = 3

[Bill Baxter]

On Wed, Jul 29, 2009 at 9:23 AM, Jarrett
Billingsley<jarrett.billingsley at gmail.com> wrote:
> On Wed, Jul 29, 2009 at 10:44 AM, Ary Borenszweig<ary at esperanto.org.ar> wrote:
>> Andrei Alexandrescu wrote:
>>>
>>> Kagamin wrote:
>>>>
>>>> Andrei Alexandrescu Wrote:
>>>>
>>>>> Kagamin wrote:
>>>>>>
>>>>>> Andrei Alexandrescu Wrote:
>>>>>>>
>>>>>>> The question is very simple: given that we're used with a
>>>>>>> specific semantics for a.b.c = 3, how can we address the fact
>>>>>>> that the semantics of this familiar operation is so different
>>>>>>> (and likely so useless) when properties replace fields?
>>>>>>
>>>>>> You're solving problems that never came to life. Well... only as
>>>>>> syntetic examples.
>>>>>
>>>>> IMHO it's quite the contrary, a.b.c = 3 is a very simple and
>>>>> concrete problem that emphatically shows we haven't gotten
>>>>> properties up to snuff.
>>>>
>>>> Never saw this problem in C#.
>>>
>>> Of course you didn't. This is because C# doesn't have it - their structs
>>> can't define properties.
>>>
>>> Andrei
>>
>> Yes they can. And also C# shows us the solution to the problem (similar to
>> what Walter proposed).
>>
>> ---
>> public class Bar
>> {
>>    public Foo Foo { get; set; }
>> }
>>
>> public struct Foo
>> {
>>    public int Property { get; set; }
>> }
>>
>> Bar bar = new Bar();
>> Foo foo = new Foo();
>> foo.Property = 10;
>> bar.Foo = foo;
>>
>> bar.Foo.Property = 20; // line 16
>> ---
>>
>> Error on line 16: Cannot modify the return value of 'Bar.Foo' because it is
>> not a variable
>
> Booom, exactly what I said about rvalues.
>

Yeh, I don't understand how any of this has anything to do with
properties.  It's the same question if you ask what should

 a.b().c = 5

 do.  It's the same issue whether you have properties or not, and
needs a solution whether you have properties or not.

--bb