Using memberspaces for a property-like syntax and more

[TommiT]

On Saturday, 2 February 2013 at 22:18:52 UTC, Jonathan M Davis 
wrote:
> [..] All these other suggestions are
> just complicating things to no real benefit.

You say "there's no real benefit". I say "there's the benefit of 
being able to add another layer of encapsulation when it's 
needed". Here's what I mean by that:

The lack of encapsulation with @property attribute:

struct T
{
     private int _value;

     void add_twice(int v)
     {
         _value += 2 * v;
     }
}

struct S
{
     private T _t;
     private int _sum_of_squares; // Can't update this

     @property ref T prop()
     {
         return _t;
     }
}

void main()
{
     S s;
     s.prop.add_twice(); // *Not* incrementing s._sum_of_squares
}

...Whereas with memberspaces we can add that extra layer of 
encapsulation:

struct S
{
     private T _t;
     private int _sum_of_squares;

     memberspace prop
     {
         ref const(T) opCall() const
         {
             return _t;
         }

         void add_twice(int v)
         {
             _sum_of_squares += (2 * v)^2; // Yippee!
             return _t.add_twice(v);
         }
     }
}