Accessors, byLine, input ranges

[Ary Borenszweig]

Andrei Alexandrescu wrote:
> Ary Borenszweig wrote:
>> Andrei Alexandrescu wrote:
>>> Steven Schveighoffer wrote:
>>>> On Fri, 29 Jan 2010 11:21:28 -0500, Andrei Alexandrescu 
>>>> <SeeWebsiteForEmail at erdani.org> wrote:
>>>>
>>>>> How is f.byLine clearer and less ambiguous than f.byLine()? Or vice 
>>>>> versa for that matter?
>>>>
>>>> Note that properties can be named things other than byLine.
>>>>
>>>> -Steve
>>>
>>> What I meant to say is that in the @property landscape the following 
>>> two conventions become suddenly attractive:
>>>
>>> * Do not use @property at all
>>>
>>> * Use @property for all nullary functions
>>>
>>> And they're bound to save a lot of time to everyone involved.
>>
>> The first post of this thread was about not invoking a function when 
>> you don't want it to be invoked. bearophile was doing:
>>
>> auto dg = int function() { ... };
>> return dg;
>>
>> but he wanted to return a reference to dg, not the result of invoking 
>> it. One way to prevent that is to never invoke functions unless they 
>> are marked with @property. Or maybe functions defined like that 
>> (closures, whatever) should always require () to be invoked.
>>
>> If that doesn't sound reasonable, see this:
>>
>> auto dg1 = int function() { ... };
>> auto dg2 = dg1;
>>
>> I'd expect dg2's type to be dg1's type.
>>
>> Let's just think a solution to this problem first. :-)
> 
> Correct. Just that I fear that it's a bit late for this all. It is 
> disheartening enough that Walter got convinced by the past discussion 
> and introduced @property without much design - after a FAILED vote no 
> less. I strongly believe a better solution is available, but everyone 
> wanted the feature so the feature just got born.
> 
> FWIW, my take for issues like the above: if a function returns a 
> function or a delegate, it can't avail itself of automatic invocation of 
> "()". That takes care of a corner case and keeps the mainstream case in 
> good shape.
> 
> I am not sure of a good solution for problems like
> 
> writeln = 2;

I think at least for the function/delegate problem, requiring () to 
invoke it might be good.

int foo() { ... }

auto dg1 = bool function() { ... };
auto x = dg1; // x is bool function()
auto y = dg1(); // y is bool

auto dg2 = &foo;
auto z = dg2; // z is int function()
auto w = dg2(); // z is int

The only thing that remains "problematic" is this one:

auto dg3 = foo; // It's int. To take the address use &
                 // but might lead to unexpected results
                 // when using "auto"