property syntax strawman

[Andrei Alexandrescu]

Marianne Gagnon wrote:
>> The alternative is to have a unique syntax for properties. Ideally, the 
>> syntax should be intuitive and mimic its use. After much fiddling, and 
>> based on n.g. suggestions, Andrei and I penciled in:
>>
>>    bool empty { ... }
>>    void empty=(bool b) { ... }
>>
>> The only problem is when a declaration but not definition is desired:
>>
>>    bool empty;
>>
>> but oops! That defines a field. So we came up with essentially a hack:
>>
>>    bool empty{}
>>
>> i.e. the {} means the getter is declared, but defined elsewhere.
>>
>> What do you think?
> 
> I liked the original idea... but this declaration syntax is a total can of worms. Like others pointed out, would the compiler automatically turn all functions with empty bodies into declarations? Would empty setters be considered a declaration? What if I actually *want*
>  to use an empty body as definition? Or what if I accidentally leave a body empty when I didn't want to?
> 
> Like someone else pointed out, existing keywords could be reused :
> 
> bool empty
> {
>     in(bool value)
>     {
>         _my_empty = value;
>     }
>     out
>     {
>         return _my_empty;
>     }
> }
> 
> I like this quite a bit.  I never wrote any compiler, granted, but I don't think it'd be that hard to implement - and doesn't introduce any new keyword.

Please, please, could we look at something that does NOT go through two 
scopes to get to the code?

> Or, alternatively, if you really wish to keep them separate, bool empty= { ... } isn't intuitive, as Andrei pointed out, but is already less error-prone than the empty-body declaration idea I believe

I think void empty=(bool b) { ... } is a net win, which the forced bool 
empty=() diminishes. It would be great to keep the setter and find 
something as nice for a getter.


Andrei