property syntax strawman

[John C]

Walter Bright wrote:
> Having optional parentheses does lead to unresolvable ambiguities. How 
> much of a problem that really is is debatable, but let's assume it 
> should be resolved. To resolve it, a property must be distinguishable 
> from a regular function.
> 
> One way is to simply add a "property" attribute keyword:
> 
>   property bool empty() { ... }
>   property void empty(bool b) { ... }
> 
> The problem is that:
> 
> 1. there are a lot of keywords already
> 2. keywords are global things

Well, property probably isn't too common a variable name, so it 
shouldn't impact existing code.

> 
> 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.

Would unimplemented setters look like this:

void empty = (bool b) {}

?

> 
> What do you think?

Looks a bit odd. Perhaps it's just the unfamiliarity of the syntax. Most 
of us got used to templates, eventually.

My own syntax suggestion requires no new keywords (contextual or otherwise).

interface INameable {

   string name {
     ();
     (value);
   }

}

class Person : INameable {

   private string name_;

   string name {
     () { return name_; }
     (value) { name_ = value; }
   }

}

In the above example, "value" could be anything the class designer wants 
- to the compiler, empty parentheses () represent the getter, (blah) the 
setter.