• Simen Kjaeraas (36/36) Apr 26 2008 I was thinking of the plans for multiple opCasts today, when inspiration...
• Jarrett Billingsley (15/15) Apr 27 2008 "Simen Kjaeraas" wrote in message

"Simen Kjaeraas" <simen.kjaras gmail.com> writes:

I was thinking of the plans for multiple opCasts today, when inspiration=

suddenly struck me. What if opCast saved its return value in a reference=

parameter of the appropriate type instead? That way, normal overloading =
 =

rules
would kick in, and you could define as many opCasts as you want. For  =

instance:

   struct foo
   {
     someType[] data;

     void opCast(ref int result)
     {
       result =3D 42;
     }

     void opCast(ref string result)
     {
       result =3D "Text here";
     }

     void opCast(T)(ref T result)
     {
       result =3D data;
     }
   }

The compiler would then rewrite as follows:

   foo f;
   void bar(string s){}

   int a =3D cast(int)f; // becomes int a; f.opCast(a);

   bar(cast(string)f); // becomes string tmp; f.opCast(tmp);

   baz b =3D cast(baz)f; // becomes baz b; f.opCast(baz)(b);


As we can see, the function call introduces a temporary value, which mig=
ht  =

be
unwanted. Apart from that, I can't see any problems OTOH, but I'm sure  =

there are
some. Please do comment.

-- Simen

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Simen Kjaeraas" <simen.kjaras gmail.com> wrote in message 
news:op.t98lo3nc1hx7vj spill04.lan...
I was thinking of the plans for multiple opCasts today, when inspiration
suddenly struck me. What if opCast saved its return value in a reference
parameter of the appropriate type instead?

...

As we can see, the function call introduces a temporary value, which might
be
unwanted. Apart from that, I can't see any problems OTOH, but I'm sure
there are
some. Please do comment.

----------------------------

No offense, but the idea is not new ;)  I'd imagine something like this 
would have to be implemented for opImplicitCast, unless Walter special-cases 
those and allows them to be overloaded on return type.  Which is weird.