Re: another way to shoot yourself in the foot?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Fri, 20 Jun 2008 23:37:11 GMT, Jeffrey R. Carter wrote:

> Robert A Duff wrote:
>> 
>> Build-in-place is determined by the type, not by the
>> syntactic form of the return statement.
> 
> I'm not sure I see any point to the extended return statement.

I agree, it was introduced solely for dealing with limited-valued
functions. IMO there should be no such thing as "limited-valued" at all.
In-place initialization should be handled by proper constructors.

> Wouldn't it have 
> been clearer and simpler to have done something like
> 
>     Result : return T;

Result : T renames return;
    -- Would be IMO better, semantically it is a renaming.

>     ...
> begin
>     ...
>     return Result;

Why this? With your syntax it is clear what is going to be returned:

function Foo return T is
   Result : return T;  -- This will be the result
begin
   ...
end Foo; -- Returns Result, obviously, as declared

> with a rule that only 1 "return variable" may be in scope at a time?

As well as that there may be no return statements returning something
else...

One problem with your proposal is:

function Foo (...) return String is
begin
   declare
      Result : return String (1..200);  -- Going to return 200 characters
   begin
      Result (1) := 'a'; -- Here the result has to be allocated
      if HALT (x) then
         return;  -- Return from Foo with Result
      end if;
   end;  -- Drop already allocated and initialized result
   return "Hallo!";  -- Return a completely different thing
end Foo;

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de