new DIP5: Properties 2

[Marianne Gagnon]

> 
> I think the poll might have been skewed due to context (forget my  
> newsgroup poll, that was worthy of an abortion, but I also didn't mean to  
> submit it :), I'm talking about Ary's)
> 
> The question was asked, what do you think this code means.  In the context  
> of D, where you know a symbol without parentheses can mean either a  
> function or a property/field, I'm certain there were several respondants  
> who didn't understand it was asking what they think is best, not *what D  
> currently does*.  Ask that same questions to C++ developers and see what  
> you get...
> 
> It's hard to phrase the question properly without bias to a group of  
> people who already know the current behavior.  Maybe something like:
> 
> Assume the D programming language required parentheses for normal  
> parameter-less functions, and required no parentheses for parameter-less  
> functions that returned a property.  For example, the following code  
> should imply a getter for a filter inside x:
> 
>      auto tmp = x.filter;
> 
> And the following code should imply performing a filtering action using x,  
> returning the result:
> 
>      auto tmp = x.filter();
> 
> Do you think it's worth adding such a capability, given that you will then  
> no longer be able to call ordinary parameter-less functions without  
> parentheses, an author of a property function must properly indicate that  
> the function is a property, and the compiler must trust the author for  
> this implication?
> 


IMP, the parenthesis thing is not about parameters vs function. I think the question is about whether the function can modify my object or not.

e.g. if I call

foo = object.x;

I assume 'object' was not modified. But if x can be like a function, disguised as a parameter, I can modify my object without knowing.

In C++, I'd say this behaviour is ok for 'const' functions. Now I haven't taken the time to study D constness, so I can't readily tell what is the direct equivalent, but I guess you understand what I mean.

In short, IMO everything that can modify my object should require () to stress that this is an action with possible side effects, not merely a getter.